Working on custom channel integration by tutorial, but my app continue disactivating

I'm developing custom application for custom channel integration by this tutorial - https://developer.zendesk.com/documentation/channel_framework/build-a-channel-from-scratch/part-5-deploying-the-channel/?_ga=2.123229901.753098886.1697466186-1432449901.1695736238

Actually it is same, I didn't add any different business logic yet, tried just to install correctly in zendesk. 

I have same integration manifest on our server. I made same admin interface, I'm trying to add account in "Channel apps" menu. It is successfully adding, but after 20-30 minutes I'm getting email that say:
Your integration with FP Telnyx Channel, FP Telnyx Channel is no longer active. Please visit your settings to reactivate the account.

And it keep occurs each time. Also I've noticed that zendesk server doesn't fetch our "pull url".

I wrote it as a ticket to support, they check everything in our account, didn't found any errors and send me here