Making backup in Twido

Problems with making backup in TwidoSoft V4.20. The PLC-program works OK. I wanted make backup into internal EEPROM of processor TWDLMDA20DRT. Chose the menu PLC>Backup, clicked it. Everything looked OK but the option Restore in the same menu was still not active. What was wrong? I repeated everything with external cartridge 32K with the same result. Tried another program (very simple) with another processor (the same type and still no success. In the software reference it is written that the program must be valid. How can I check it? The option: Analyze program did not give any errors.