Account refuses to use GPT 5.5

For a few days, my system properly updated and used ChatGPT 5.5 following the rollout, but for some reason since then it’s swapped back to using 5.3 for normal conversations and 5.4 Thinking for advanced thinking. Responses to conversations, even those that it generated with GPT 5.5, say they are made with GPT 5.3. Regenerating GPT 5.5 responses now generates them in GPT 5.3. New conversations use GPT 5.3. It’s been stuck like this for at least a week now. I’ve tried logging out and logging back in and clearing my cache, neither of which works. I know this isn’t universal because my second account uses GPT 5.5 no problem. Is this happening to anyone else? How do I get it off of 5.3?