The problem seems to be that the UTXO simply isn't available anymore in core, because the transaction is already sitting in your own mempool.
Due to the missing internet connection, however, it didn't get broadcasted and therefore no other node is aware of this transaction.

You can either publish the raw transaction by yourself, as mentioned by BitMaxz or you can start core with the argument -zapwallettxes.

2020-08-17 11:11:11 (ERROR) -- Traceback (most recent call last):
  File "/usr/lib/armory/ui/TxFrames.py", line 948, in createTxAndBroadcast
    ustx = self.validateInputsGetUSTX()
  File "/usr/lib/armory/ui/TxFrames.py", line 902, in validateInputsGetUSTX
    lockTime=TheBDM.getTopBlockHeight())
  File "/usr/lib/armory/armoryengine/Transaction.py", line 2513, in createFromTxOutSelection
    return self.createFromPyTx(thePyTx, pubKeyMap, txMap, p2shMap)
  File "/usr/lib/armory/armoryengine/Transaction.py", line 2414, in createFromPyTx
    cppPrevTx = TheBDM.bdv().getTxByHash(txhash)
  File "/usr/lib/armory/CppBlockUtils.py", line 1662, in getTxByHash
    def getTxByHash(self, *args): return _CppBlockUtils.BlockDataViewer_getTxByHash(self, *args)
DbErrorMsg: <CppBlockUtils.DbErrorMsg; proxy of <Swig Object of type 'DbErrorMsg *' at 0x7f4929064300> >

2020-08-17 11:11:37 (ERROR) -- Traceback (most recent call last):
  File "/usr/lib/armory/ui/TxFrames.py", line 948, in createTxAndBroadcast
    ustx = self.validateInputsGetUSTX()
  File "/usr/lib/armory/ui/TxFrames.py", line 902, in validateInputsGetUSTX
    lockTime=TheBDM.getTopBlockHeight())
  File "/usr/lib/armory/armoryengine/Transaction.py", line 2513, in createFromTxOutSelection
    return self.createFromPyTx(thePyTx, pubKeyMap, txMap, p2shMap)
  File "/usr/lib/armory/armoryengine/Transaction.py", line 2414, in createFromPyTx
    cppPrevTx = TheBDM.bdv().getTxByHash(txhash)
  File "/usr/lib/armory/CppBlockUtils.py", line 1662, in getTxByHash
    def getTxByHash(self, *args): return _CppBlockUtils.BlockDataViewer_getTxByHash(self, *args)
DbErrorMsg: <CppBlockUtils.DbErrorMsg; proxy of <Swig Object of type 'DbErrorMsg *' at 0x7f49291c6c60> >

They are the same company. Leupay was rebranded to Leopay: https://blog.leopay.eu/leupay-becomes-leopay/

I also recall seeing reports of people saying they weren't crypto-friendly, unsure of that's still true today.

Still not worth it, my friend. In fact, I'm still not sure any amount of interest is worth it, and that they're actually lowering interest rates is a sign that even they can't make as much as touted.

Anything guaranteed just sits uncomfortably with me, because there's no such thing. Like I said, though, if deposits were insured, like they would be in a bank account, that's a different story. That's what you should find out (and I'm more than certain they don't).

The service I'm talking about is freebitco.in. Probably the oldest faucet around? That's the same risk I'd say, putting your money and hoping they never run away. They've never scammed, but past performance isn't a guarantee of future, right?

@hashtag
There is a new EMI for european citizens. You get an IBAN number and you can order a plastic mastercard. You can top up your balance with card, exactly like what you're looking (for free). I verified my account this week and I tried 3-4 times to do it, it works very well.  
The android application is Yeeld

If your deposits are insured, then sure why not? If Japan's able to enforce deposit insurance on licenced exchanges, surely a Gemini-backed entity must be able to do the same, especially if they're soliciting your deposits.

2% annual interest is not worth the risk, as pointed out. If you REALLY wanted to gamble, there is a service here that lets you earn about 4% annually (compounded), crediting you daily, and funds never locked. Hint: They're in Gambling section and are one of the most read and responded to threads. They've not scammed anyone for 4? 5? years but I wouldn't store my precious savings for that kind of interest. A little here and there, sure.