My RM9 will not open a .RMbackup file

Having made a mistake I thought I would go back to the most recent backup. But it said it could not open the file. What am I doing wrong.

Use Restore from Backup, not Open.

From HELP

Restore a Backup

Many many thanks to Bob and Tom. So simple but until you have it pointed out and learn something new it was a complete black hole. Just shows the value of the community.
Birdie