I can also confirm that I am getting the same error.
I can still do New Chats but I get the error when trying to open existing chats.
I am also not able to open up My Plan as I was trying to see if a payment was missed possibly.
I can confirm that this error exists using ChatGPT on all my devices that are on different OS platforms, browsers, and internet services (VPN or Not).
I have no issues when accessing ChatGPT via API.