Help with recovering STRAT and converting to STRAX

Hi there, I haven't really payed attention to the coins after I purchased them back in 2018. Now I see that I need to swap them from STRAX, etc... Here's my problem: I have the 12 word seed. I can also restore it in the Electrum Stratis wallet (that I used back in 2018), but that wallet won't connect to anything (I guess b/c it's deprecated and the servers are offline by now). But no problem I thought: I can just import my seed into the Stratis Core wallet. Said and done -> no coins appear in the wallet. I checked the addresses that are being generated and those are different ones then those that the Electrum Stratis wallet generates from the very same seed words. What am I doing wrong? As another option, I also have the plain private keys for the addresses. But I can't find any way to import those into the Stratis Core wallet. Any help on this one? Thanks, Goddchen