Hello,
For some reason when I apply changes on the Edit Album: Images page on the backend nothing works and I m automatically redirected to my homepage.
I can't change Title Names etc etc.
What can be going wrong?

Best.

Jacobo.

Are you using the latest Zenphoto version? If not please upgrade. Also please review your Zenphoto and server error logs:
http://www.zenphoto.org/news/general-contributor-guidelines#reporting-bugs

I am using the latest Zen Photo version. And the Basic Theme.
I only changed the theme code to customize it.
the only error that appears on the log is:

NOTICE: Undefined variable: zenCSS in /home/espaciov/public_html/exposiciones/themes/basic/index.php on line 14
include called from include (index.php [130])
from index.php [28]

Not related to the problem. As I said before the only error I have is when I apply changes on Albums << Edit Album << Images the page redirects me to the index page (www.espaciovalverde.es) where there are not image galleries at all...
weird...

Did you also look at the server PHP error log as well? That might have more errors/notices noted than Zenphoto own log. It might be a an issue with POST limits on submitting the form for some reason but just a guess. Maybe the POST limit is set too low on your server.

I only find this two errors on the log...
But seem to be from another date...

Ive changed the php.ini to report errors but they dont seem to show...

[09-Jun-2017 17:12:51 UTC] PHP Fatal error: Invalid image instantiation: file does not exist in /home/espaciov/public_html/exposiciones/zp-core/class-image.php on line 145
[09-Jun-2017 17:12:52 UTC] PHP Fatal error: Invalid image instantiation: file does not exist in /home/espaciov/public_html/exposiciones/zp-core/class-image.php on line 145

That would likely result in a blank page actually. If that happens often you need to use the "Refresh the Database" button. Remember zp is filesystem based and the database mirrors that but can get out of sync. Normally that is covered by visits to front or backend.

However I don't think that is your issue. I am sorry, I have no idea right now.

Another strange thing that happens, when I press "Apply" a lot of times (before the server redirects me to the homepage) the server bans my IP and I have to connect to my webpage through a proxy or vpn.
Weird... Weird...

I found the problem: Modsecurity. I deactivate it on Cpanel and everything works.
[SOLVED]

Ah, good you figured it out. Now that you mention it I have a far memory of various issues caused by too strict modsecurity settings several years ago.