Issue upgrading from 1.9.16 to 1.10.1

Hello all,

I have really bad problems with upgrading from 1.9.16  to 1.10.1.
I have running a LAMP-Server (Linux, Apache, MySQL, PHP) with the following version:



osTicket Version     v1.9.16 (f4a172f)
Web Server Software     Apache
MySQL Version     5.5.58
PHP Version     5.6.30-0+deb8u1

I did a snapshot with VMware of my virtual machine (to get back to the running version before upgrade) and followed this instruction, as recommended:
http://osticket.com/wiki/Upgrade_and_Migration

... Copied the upload-folder to the web-folder... overwriting the existing files... restored the old ostconfig.php...

BUT everytime I try to reload my website (in order to run the upgrade-wizard) I get an error! OSticket isn't running anymore (www.webserver.de). Further: If I try to open www.webserver/setup, the system responds, that OSticket is already installed.

I can also provide some logs if needed. (but which?)

Can somebody help me here? I spent a lot of time with troubleshooting.. without any success. I'm confused. :(


Thank you very much for help!
Samuel