Not a valid license file, license file extension shall be rlf

yd008
yd008 China

Recently, I tried to restore the backup of the field robot in Robot Studio, but kept reporting the error "Not a valid license file, license file extension shall be RLF" in Robot sudio. Here is my attempt.

1. I have changed the Robot Studio version. I have tried both 6.08 and 2021.2 versions, but the same mistake still appears

2. The Robot ware version is the same as the field robot version

3, I used the other 3 computers and tried to recover in the virtual machine, but it didn't work

4. I tried several different field backups that used to be recoverable, and now every one of them is reporting an error

5. The system I created with Robot Studio is backed up on the computer, which can be restored in software