After update no access to previous backup files

Hi all,

I updated to build number 6613 which seemed to be successful. Afterwards Acronis couldn't continue with differential backups based on previously existing backup files on a ftp server. Further, Acronis refuses to make recoveries from existing backup files.

The ftp connection seems fine since Acronis can write new backups to folders on the ftp server. It just "refuses" to use the older backup files and shows an error message that the backup files are not accessible. Further, the ftp server doesn't seem to be the problem since no changes were made to the ftp server for a long time before or after the backup.

My next steps were to delete the backup configuration and recreate it by adding one of the previous existing backups. The *.tib backup files are shown but the "add" button is grayed out when selecting one of the backup files. This is the case for all existing backup files.

Further, I completely deinstalled Acronis TI 2015 and reinstalled it by choosing to download and install the latest version. The previously described problems still persist.

What can I do to continue with differential backups based on the previous backups and to extract files from the backup files?

Thanks a lot for help!