Panel does not work "Couldn't load variables.txt?aldope=85908"

I have just instaled Distro and I can’t enter panel. When I try I get message “Couldn’t load variables.txt?aldope=XXXXX”

I have created new, empty file variables.txt in /var/www/html/panel.
Then I have entered [Advanced Settings] section [Flash Operator Panel] and set [Start FOP with amportal] to True.
After Applying Configuration Changes I have got the message that OP Panel cannot be restarted in [FreePBX System Status] section [FreePBX Notices]. After restarting the box PANEL seems to be working!