Howard Miller

Moodle 4.1...

"PHP version: minimum PHP 7.4.0 Note: minimum PHP version has increased since Moodle 4.0. PHP 8.0.x and 8.1.x are supported too"

PHP 7.4, 8.0 and 8.1 are supported. Nothing else is.

Moodle 4.5....

"PHP version: minimum PHP 8.1.0 Note: minimum PHP version has increased since Moodle 4.3. PHP 8.3.x is supported too"

So, 8.1, 8.2 and 8.3 are supported. Nothing else is.

Have you checked 'upload_max_size' and 'post_max_size' in Site admin > Server > PHP Info? In each case BOTH columns need to say 400M

Assume you mean.... https://moodle.org/mod/forum/discuss.php?d=466999

(In Moodle) Site admin > Server > PHP Info

Near the top is the list of .ini files that were loaded. Is the one you changed included?

If so, on the same page, find upload_max_filezsize. What does it say (both columns)?

My life is complicated

Yes - we use Docker for development environments but we use Git extensively for tracking the code. I'm not sure I use all the features I should/might. I'm still very frightened by submodules :-O