The problem is in the supplied UploaderController.php file.
Replaced the file with the LS3 one and have fixed the problem.
However, this puzzles me as it should have worked with the freshly installed file.

Actually not fixed - only partly fixed. But it appears the problem is in that file. I cannot JUST replace the file. It appears to be in the MIME checking section

More data - the file from LS3 will accept the file, but the save button does not work.
the file from LS4 will not accept the file. Because these installations are in peer directories and using the same PHP from the server it has to be a problem in the LS4 and not in the PHP itself, right? This has me stumped.

But it appears the problem is in that file.

What file ?

1. Screenshot of error message?
2. Which files did you try to upload?

From the beginning:

We have an instance of LS3 (Version 3.22.4+200212 ) that is working perfectly. In a peer directory we have an instance of LS4 (Version 4.1.4+200214 ) that was a fresh install to an empty database. Everything is running on the same server with the same PHP and the same database server.

When I attempt to upload ANY file on LS4 it gives me an error that it cannot handle a file with that extension. See the screenshot LS4file.jpg below. I took the /application/controllers/uploaderController.php from the version 3 site and copied it to the version 4 site. What I get is screenshot LS3file.jpg when I try to upload a file. It appears to understand the extension correctly. However, because the uploader.php file is not really for LS4 the "Save Changes" button does not work.

I compared the two uploader.php files looking for something that might be blocking the upload and tried a variety of edits thinking I could isolate the specific cause, but I have not been successful.

Because my LS3 works fine I think the PHP settings are all correct. Where else should I look?

LS4file.jpg (45,201 bytes)   

LS4file.jpg (45,201 bytes)   

LS3file.jpg (69,421 bytes)   

LS3file.jpg (69,421 bytes)   

This error is due to JS not to PHP.

But it appears the problem is in that file.

Bad comprehension ; you spoke for UploaderController.php, not for a file to upload.

There is something in js console ? (We have a forum post with this issue too : js issue, no PHP)

Sorry - that is why I repeated everything.
Do you have a reference for the post "We have a forum post with this issue too : js issue, no PHP"
I cannot find it.

What would I look for to fix the problem? Is there a solution?

Thank you for the ongoing help.

Before see the page with the upload question,
Activate console (F12) on your browser,
See if there are error.

Attached is the error. I cannot find the directory within /tmp where spectrum.js is supposed to be located. This is a fresh install of Version 4.1.4+200214. The directory within /tmp did not exist.

I did a search and found spectrum.js located in /assets/packages/themeoptions-core.
I made the directory in /tmp and added a copy of spectrum.js

Now the error is different as seen in uploaderror2.jpg

You can access the survey at
https://guernseyresearch.com/survey/index.php/794574?lang=en

I am using Windows 10 with Firefox 73. I am not an expert in this so I am really stuck.

Browser related issue
Checked with Firefox : OK

Capture d’écran du 2020-02-15 18-11-31.png (70,193 bytes)   

Capture d’écran du 2020-02-15 18-11-31.png (70,193 bytes)   

I don't understand. Which version of Firefox? I see in the responses that the file did actually upload.

Note: this was after I manually add the directory and script file. (uploaderror.jpg)

Did not work with Google Chrome ( Version 80.0.3987.106 (Official Build) (64-bit) ), see attached
It does not work with MS IE, It does not even get to the upload question.
MS Edge was the same as Chrome.
or with my updated Firefox (73.0 (64-bit)). see attached

We cannot ask customers to use alternate browsers.

I tried changing the theme and it had no impact

upload-chrome.png (87,148 bytes)   

upload-chrome.png (87,148 bytes)   

We just tried Chrome on a 32-bit machine and had the same error.

Firefox 68.5.0esr (64 bits) (Debian)
Midori 7.0

BUT : ok with png, not with jpg.

Can you test with gif, pdf, png etc .... files too ? Maybe only jpg ? (jpg == jpeg)

We use jpg and dif mostly for this survey. Occasionally a tiff or png
I have been testing with jpg and pdf as those are key to our use. They do not load.

FOUND IT!
The default file types for the file upload question for a new survey have spaces between the file types, which is not correct. Once you change the allowable file types they will be used as the default for future surveys. Because there was a space after the first file type it was the only one allowed. I needed to remove the spaces between the file types. Once the list of default file types was fixed it will work for all future surveys. It appears to remember the list you prefer even when creating a new survey.

There is a need to ensure that the defaults for a NEW INSTALL do not have spaces.

default.jpg (50,690 bytes)   

default.jpg (50,690 bytes)   

Great !

My opinion : we must explode and trim !

Thanks a lot, i take the issue

Nice found

LS 3 does this correctly even when there are spaces in the extension list.

@cdorin : sorry, i only have my laptop actually

I can not fix it without buold and don't want to setup builder on my little laptop ....

Fix is
return col || ext.toLowerCase().trim() === item.toLowerCase().trim();

at https://github.com/LimeSurvey/LimeSurvey/blob/f65418b1083ff653a9a13e5362e7e06628f5958d/assets/packages/questions/upload/src/uploader.js#L150

Good catch @GuernseyResearch!

I can confirm that spaces caused no hamr at LS 3 so this is a regression that should be fixed soon. Otherwise there will be lots of support requests.

@Mazi : if you have yarn and composer : see the line to fix if you can do a pull request :)

I too have this issue using LS 4.1.6+200220

Is there a file that can be edited to delete the spaces in the extension list, as when i try to edit within the question editor it always defaults back when saving (this also means i cannot add media file options (eg mp4, 3gp etc) like i could in a precious version (LS 3x.

In addition to this the file upload limit also keeps defaulting to 10240, when it should be 200k on my install (240M + on PHP upload limits)

Never had any issues using a earlier version of LS.

Related to https://github.com/LimeSurvey/LimeSurvey/commit/782da7211ddd619c03a2d4ae736a625949619b8c#r38952884 :)