Using Same Username on Two Computers (at different times)

[cdubs14]

Hi,

 

I'm running a Tekkit Lite Server on a Raspberry Pi 4. Up until now (one year) I have had no issues, and I connect to play on the server via my 8 year old MacBook Pro. I recently built a gaming PC and would prefer to play on that hardware instead, but run into the following problem:

I can add the server and it shows up with the proper description & info, but I get the attached error every time I try to connect. I've read up on this problem and tried every possible fix (mainly with Java, enabling IPv4 through both CMD and the Technic Launcher Settings) but still have not had success. I figure this error has to do with using the same login on my Mac as on my gaming PC, but I'm not using these two machines at the same time so it shouldn't be a problem. Just to try something, I even erased my player data and then tried connecting via the gaming PC, to again get that same message. I'm running Windows 10 with Java 8. Any help would be greatly appreciated!

Thanks