Hi Jana K.,
If you mean that the bank statement file that you use is correctly formatted and this issue has been happened after version updating, the issue can be related to the broken GER template. Please try following steps if it applies to the sandbox environment and to check if you can import the file:
1- Run "Restore broken templates" (Organization administration > Electronics reporting > Restore broken template) and wait that it get completed successfully go to
2- Import the bank statement. If you get the same error message, go to step 3
3- If you use standard configuration, delete Bank statement (RU) and its related model mappings and Payment model
4-Delete your user data and perosnalization
5-Log out from the solution
6-Open Private or incognito browser and import Bank statement (RU) from Microsoft Repositories
7-Import the bank statement
I hope it helps!