Check in the control panel of your server which version of PHP you are using and which version of the photo plugin because there are some combinations to which this happens.

Check also in the permissions table for user roles that have access, there are some old plugins still in the store that according to what other installed plugins the combination clears this table.

I suppose you have already tried to put it in developper mode and checked that no error occurs.

I can not think of any other check at a general level, not help more without being able to access the web and FTP as admin, to see if you can not find the photos due to any problems with permissions or directory names, or something like that.

There are several plugin developers that can help you with this because it should be a simple problem.

Choose one of your confidence because these access data will be needed. Some charge and others not for this type of aid.

 solved ow_userfiles/.htaccess Instead of Options All -Indexes, write Options -Indexes

thank you Patricia