Member cannot upload any picture

Hello,

I have just installed the plugin and now trying to finally configure it.
An issue occured while testing – I cannot add any photo as a logged “member” user. My account is activated, works ok. The problem repeats for every upload settings.
An error messsage is “Forbidden” or “image too large” (when I set max img size to 500 000 bytes and try to upload a ~300kb jpg file).

The site is working on this server for a year, everything is working well, also adding media to the WP library.
My WP is in the latest version, also there is not any plugin conlict.

Could you give ma any clue on how to make it work?

Greetings

https://www.ads-software.com/plugins/ultimate-member/