Galaxy S9 won’t update.

My phone won’t update beyond android 8.0. I purchased my s9 (certified refurbished) via amazon in 2018. I live in the caribbean and upon receiving the phone I had to contact amazon for an unlock code in order to use the phone. At first I had no issues updating the software as I believe the phone was updated twice before android 8. I noticed after a while that my phone had stopped updating. I never paid it any mind until Bixby updated and I was unable to install it because my software isn’t up to date. I have tried using smart switch. I have done a virtual battery pull and I have wiped the cache partition. I am willing to do a factory reset but I have seen a few people on various sites who had the same issue but it wasn’t fixed with a factory reset. How can I fix this?