Receiving grin "transaction doesn't exist"

I’m new to Grin and wanted to play around a little with the floonet before going on the mainnet.
So I got some Grin in my wallet and wanted to make a transfer.
So I sent 10 Grin with a transaction file, took this file and received it on the same computer, all went well. Now I got a transaction.response file that I have to apply to finalize the transaction, right?
This step won’t work and idk why.
The error says:

Wallet command failed: LibWallet Error: Transaction xxx doesn’t exist

I can see the send transaction as confirmed with a confirmation date in my wallet, but the receiving transaction is still not confirmed. What can I do to get my Grin back?

Tried to send it to another computer with the file, so it’s not on the same computer and wallet. Still doesn’t work. Same error.

Best Regards,