Hey @Rupa Kapoor64, sorry for the trouble! There is a known issue with ClickFunnels where they often times have delays when sending an email address from ClickFunnels to Convertkit through the API. Unfortunately this is not something within our control, as ClickFunnels built the integration. (The delay can be anywhere from 5 minutes to 60 minutes.)
Is it possible that this delay was the culprit, and those subscribers came through eventually?
If not, given that it was working at first and then stopped, I'd recommend reaching out to the team at ClickFunnels about this first — since they developed the integration, they are likely to have more visibility into what might not be working correctly, and should be able to help with troubleshooting further :)