I suggest the seed phrase he's using now is from a fresh wallet created with the 3.3.8 Appimage, an empty wallet. The seed words for accessing the coin in the older version Electrum wallet are somewhere else, or lost. This contradicts his claim that he has the right seed words. In the absence of proof and 19 months passage of time, it's more likely than any other guess, in my opinion
I would tend to agree... unfortunately, none of us except the OP were there... and know exactly what has transpired. To a certain extent we have to take the OP's word for what they did and what information they have... and that the information they are providing is true and correct.However, a set of 12 seed words doesn't magically start producing different wallet addresses.
So, it's either the correct seed and some other variable like the seed extenstion phrase or derivation path has changed or "BIP39 seed" option was selected... or the seed is just wrong.
¯\_(ツ)_/¯
I wish the OP the best of luck, but there really isn't anything "new" to suggest at this point...
