Pm me access to your super admin in order to enable FPSS and check out what is going on...

All your permissions are wrong!
Please install Admin Tools from www.akeebabackup.com/ in order to fix your permissions as they should be and then reinstall the extension.

Nope, that didn't work (as I expected). The problem is in the upload of images (either thumbnail or big imate).
The animated circle keeps running and if I go back with my browser, I get this error:

{"type":"thumb","error":"This is not an image file","preview":"","value":""}

This has nothing to do with wrong set privileges but is a programmer issue.
Jmblr

Of course it does! Please contact your hosting company and ask them to fix your permissions asap.
The extension has not installed correctly. That is why you cannot see the parameters. In addition check the Requirements in FPSS documentation.

Which permissions do you refer to; as from which folders (too vague).
Thumbnail images is generated and put in the Cache folder. The big image itself though keeps the upload busy.
Are there J! related modules or plugins necessary that are in J! 2.5.x but not in j! 1.5.6?

I spent also some money on obtaining Akeeba Administrator, fixed the permissions and that's it!
My hosting provider has checked them and they all are found well.

Some months ago I suggested that you implement a debug function in FPSS so that in case of a problem we can see what really is the problem here.

Regards,
Jmblr

Admin tools is a free extension!

Not the Pro version.

I haven't asked you to install the  pro version.

No, that is correct. I only complaint about FPPS for J! 1.5.26. The rest is my concern.
Can you please provide a solution before the weekend?

Jmblr

I told you that your permissions are wrong and you need to fix them.