Elastic Beanstalk Error deploy python flask application sqlite3

I deploy flask application on Elastic Beanstalk, I am getting 502 gateway nginx/1.20.0, error in browser when i was sending the request through browser when i checked the nginx error log, i got this error /var/log/nginx/error.log - "...Connection refused) while connecting to upstream, client:...". Elastic Beanstalk - Enhanced health overview: Severe 100.0 % of the requests are failing with HTTP 5xx. ELB processes are not healthy on all instances. ELB health is failing or not available for all instances. Impaired services on all instances.

100.0 % of the requests are failing with HTTP 5xx.
Process default has been unhealthy for 22 hours (Target.ResponseCodeMismatch).
Following services are not running: web.