Internal server Error or The server is temporarily unable

This happens to me.

I run a script in PHP, what it performs is a conversion of tables in the database, I used this script in the past, and it didn't give me any problems (in the same database) but... I used another panel.

Well, if I configure it to use php-cgi, at one point I get "Internal Server Error", if I configure it to use php-fpm, at the same point I get "The server is temporarily unable..."

And I've been dealing with this for many hours, I've tried everything I can think of and found, but I can't solve it.

Any idea? I'm starting to get a little desperate, to say the least...

PS: No errors in the apache or mysql log

try temporarily dropping the CSF firewall. or upping your connection limits on mariadb if your PHP script makes many DB calls.

try temporarily dropping the CSF firewall. or upping your connection limits on mariadb if your PHP script makes many DB calls.

I appreciate your response.
I made so many, so many changes to my account, that today I had to rollback a snapshot,,,
I didn't think about deactivating the CSF firewall, but I didn't get any notice or alert either.
Indeed, the script makes modifications to the database but... it does not "break" the mysql service either...

I just checked my my.cnf file and I don't have any max_connections value set, I'm going to see if I can see a way to know what value is set by default.

But...the script, I don't think it makes many calls, it is an old script, I have to run it at most in php 5.6 but...4 years ago I used it, without problems, on another hosting and panel, but without problems, with the same database as now...

It doesn't cost me anything to try those two things, but I'm afraid that...

If I use php-fpm the response is a 503 error, if I use php-cgi the response is 500 (always at the exact same point).

If it can do anything, I prefer the max_connections of the database, because for php, I have already given everything to the maximum even...

I say it, I really appreciate your response.