Excel App opens old Version of document saved in Sharepoint Online

[DaveZ2022]

I am not quite sure if It's a sharepoint online or an excel problem. If I open the excel document with the online excel version, it will show me to correct last saved version of the document. If I open the document with the app (excel program on my computer) it shows me an old version with the hint that there is a new version on the server. Any suggestions inside the program to solve the problem don't work. It will still open an old version. 

Do you have any suggestions for me?

[#2]

Sounds like a file sync issue. Do you have the library sync'd to your local computer? Check the OneDrive client to see if there are any file sync issues.

What happens if you right click the document in the Browser and choose Open with App? Does that open the correct version?

[#3]

The file (library) isn't sync'd to the computer. When I click the document in the Browser and choose Open with App, it will show an old version, when I choose open in browser (the online version of excel) then I'll see the correct version.