Last year, I thought my TSP was an IRA. Now I'm getting an error with this year's taxes. I tried to amend last years taxes, and it got rejected.

I keep seeing "IRA Contributions Worksheet: Line 26 - Taxpayer's excess Roth IRA contributions credit should be equal to $..., the Roth IRA contribution credit from Form 5329, Part IV. I keep putting 0 in line 26 and on the top and nothing happens.

I asked this a bit ago and someone recommended me amending last years taxes as I put that I contributed to an IRA when I was contributing to TSP (military’s retirement fund) that I thought was considered an IRA. I submitted the amendment and it got rejected. I want to call an expert, but I'm living in Japan right now with a Japanese phone number. The website wouldn't accept the Japanese phone number format and I'm at a loss of what to do. Is there any chance that someone can help me this issue? I tried seeing if I can submit another amendment, but this time it had me download an app and it gave me a bunch of weird technical errors. Any help would be much appreciated and put my mind at ease as it's been stressing me out a ton.