Have I been discriminated against getting training at work

Hi was wondering if anyone could help with this question, in England

I have been employed with the company since 2017, was diagnosed with graves desease in 2019 and been on medication since then, unfortunately last year the medication stopped working and I had surgery to remove my thyroid and was off work for 6 months and now require medication for life.

I am back and work and there was an opening for extra training and qualifications to be able to get a pay rise. I applied for it but have been told that I was not selected due to not being in there criteria (no incidents at work, positive reviews, sickness etc over the past 3-6months) they told me they have no records over the timeframe required but everything before my time off I would have been more seriously considered, I accepted this but starting to think have I been discriminated against as I believe my condition being a lifelong condition is protected under the equality act?

My manager was unhappy about the outcome it as he feels it’s unfair but I just want to see if I can help him raise it to our HR department.

Happy to answer questions or be proved wrong Thanks