Hi Petras,
It sounds like you need to talk to a distributor but for some reason don't have one.
Do you have the .dat and .ref files installed in the folder : Library/Application Support/Sinar eXposure/Sinarback LV75(or whatever your back is called here)/ ?
They should be on the disk that came with your back.
Apart from that, I'd be trying complete reinstall, or ring Sinar rather than wait for an email.
Regards, David