Thumbnails Regeneration problem

[Sinius]

I tried to regenerate thumbnails through BO with
Select Image: All
Erase previous images: checked (yes)

Presta says that images were regenerated successfully, but there isn't even ONE regenerated file when I check through FTP and ofc there are none shown in FO. I got around 20,000 images to be regenerated and all of them are ending with "_". Is that a problem?

I've tried to regenerate only Products and Large, with erase turned off or on and the result was the same (none).

Should presta generate thumbnails immediately or does it take a while?

Many thanks for answers

[Kalastudio]

Hi,
Take a while but looks like there are some errors.
Please check:
1. Permissions Folder
2. Increase the php timeout settings on your server.