ok, I spent the whole night and figured it out. Might be helpful to someone else who is having the same problem:
Look at the 274th line in the plugin file:
if ($user_info->wp_capabilities[‘file_sharer’] == TRUE)
This “wp_” in “wp_capabilities” is actually the wordpress table prefix. In my case the table prefix was “wp_ast_”. So what I did was I changed the code a bit from
if ($user_info->wp_capabilities[‘file_sharer’] == TRUE)
to
if ($user_info->wp_ast_capabilities[‘file_sharer’] == TRUE)
Now its working perfect ??