I've also been having issues very suddenly
I can get everything connected with Zapier, can even run the test through Zapier and everything works great. However, it will not trigger when a new form is submitted. No errors shown in Zapier, and the form sends to other storages just fine.
Very frustrating as this sudden issue has caused me to miss opportunities to reach out to clients quickly, and likely miss business.
I am not sure if this has any relation to what was previously discussed in this thread, I didn't understand much of the technical discussion. Other than, it appears that SS is not communicating with Zapier properly.
Hope this adds some nugget of information to the issue and is resolved soon.