I spoke to QuickBooks support today, looking at this same problem. Before calling them, I had read this thread. I performed the following before making a call:

• Test using Safari
• Test using safari after clear cookies and cache
• Test using Chrome / Brave
• Re-test clearing cookies and cache
• Test using Firefox
• Re-install Firefox totally.

Despite the above, this was still broken. So I called support. The support agent screen shared, saw the problem, and went away to the "back of house" team to find an answer. I got a call back later. They said they could not replicate the issue and wanted me to delete and recreate the rule.

I did some further analysis myself. Instead of deleting the rule, I created a new rule with a split, and it worked. I then exported the rules, and started comparing the differences between the non working rule and the working rule. After some time and testing, I confirmed that this bug ONLY happens if you have a rule that has a SPLIT transaction, where you set the Payee for the transaction. Under those circumstances, it fails.

The support agent was able to go away and replicate the fault, and then tried to tell me that I cant set a payee, because that will affect the criteria for the match of the rule. While I can confirm the auto add then works, that is certainly not a solution. I told the agent it was a bug, and needed to be fixed. They assured me it was not a bug, and everything was working as expected.

I did not accept that explanation. Why would the Payee field not be greyed out if completing this field will break the whole functionality of auto-add. I am currently waiting on someone to call me back, but that was a less than ideal support interaction.