So, if I've understood correctly: you received coins from Bisonapp (a custodial exchange), and they did show up to your Umbrel balance. Then, you received money from Bisonapp again, and they did show up, but disappeared a little later.
If that's the case, then did the transaction confirm the second time? If it was unconfirmed, then it might have been double-spent after you looked at it last time. You need to contact Bisonapp.
Since umbrel gives a new address for every transaction I am guessing (100% guess) that the address the OP gave was the next one in his wallet, which would be the one that is showing now. Even if the TX is double spent or dropped it does not display the old addresses. Umbrel also keeps the default size for the mempool. So it's entirely possible that since transactions with under a 4 sat / vb are being purged at the moment, that it *was* sent, and *is* out there BUT his node does not see it. And unless the OP has it someplace there is no easy way to see what the old address was unless he gets it from Bisonapp. You can get it by sshing into umbrel and using bitcoin-cli and get it from there but I have no idea how to get it from the GUI.
-Dave