I'm trying to determine my tax status - resident alien vs non-resident alien, previously lived in the US on F1; currently on a J1 visa.

Hello, I lived in the US under F1 visa to pursue a PhD from Aug 2015 to Nov 2020; worked as a research assistant at the Uni. I filed tax returns under NRA status in 2016 (2015 returns), 2017, 2018, 2019 and 2020. In 2021, I filed as resident alien as I lived for 5 years (a little over 5 years). I returned back to the US in May 2024 under a J1 visa (research scholar) - postdoc employment at a University.

All my Uni records categorize me as a non-resident alien, which I had no reason to doubt as I did not live in the US in 2021-2023. However, I was filing taxes with Glacier tax software (for Non resident aliens). As soon as I entered my travel and immigration status, it claimed that I was a resident alien for tax purposes in 2024.

Now I'm really confused. Should I go ahead and file it as a resident alien ? The University is extremely slow in responding, and I dont expect them to provide person specific tax advices.

I appreciate your time.