Okay, with 644 the user name you use on connect must belong to the group of Owners or you don't have permission to upload files.
If you have access to a second FTP server, you should check if you can upload files to this server to determine if the problem is on server side or on client side.
If you are using a firewall on your Mac, it is possible that the firewall blocks the upload. Perhaps you have granted the previous version of UEM to pass the firewall in both directions, but have not yet set that for current version of UEM. The really good firewalls do not manage the rules for applications on an application name only base, but take the version of the application (and the CRC of the executable) also into account. You may try use Passive Transfers which is an option in the FTP account settings.
Possible is also that something is not correct installed. Reinstall UEM and check if that helps.
If all above does not help, then I suggest to contact IDM support by email and attach the file containing your FTP account settings and include also the data for setting up the connection so that IDM can try connect to your FTP server, download and upload a file and verify if the problem is caused by UEM itself.