Puzzle progress no longer saving

[chillywillysoft]

Describe the bug
Until about a week ago puzzles I was solving would save the progress. If I closed the browser and then went back to the same puzzle I could continue where I left off. About a week ago it stopped saving the progress. Interestingly, puzzles I started solving before one week ago will still restore the progress and if I make changes to them then the changes will be saved. But on a puzzle I have not worked on before one week ago, it will not save any changes in progress. (As if it can read and modify old files but can't create new files.)

Desktop (please complete the following information):

• OS: Windows 7
• Browser: Firefox
• Version 115.16.1esr (64-bit)

Additional context
The timing of the issue seems to coincide with an update to Firefox on Oct 1. I am on the extended support release (esr) branch whose release notes are here. It is probably a subset of changes made to the main branch whose release notes are here. Maybe these changes are related: "SameSite=None cookies will now be rejected when there is no Secure attribute included." and "Support for Cookies Having Independent Partitioned State (CHIPS) was now added"

In Firefox's privacy settings I have added Tracking Protection exceptions and Cookies and Site Data exceptions for "https://gmpuzzles.com" and "https://swaroop92.github.io" but it does not help. I am not running in private mode.