Engagement is dead. Start again?

Instagram these days is really punishing your account if you don't post consistently every day.
The problem is, as you said, that you haven't published anything in a month.

I've seen this problem countless times, and the only solution is to start again to publish and interact with your followers every day.
If you stick to it and don't miss a day, in a few weeks, everything will be back to normal (even more if you post high quality and relevant content and hashtag).