The reason for the cancellation of Turkish flights was the observance of health protocols

Reza Jafarzadeh, spokesman for the National Aviation Organization, announced; 

During the period of coronavirus outbreak and cessation of flights to different countries, each country takes different measures to establish or lift flight restrictions according to its health status and that of the other country. 

This postponement of the flight permit by Turkey was only in line with the observance of health protocols and the prevalence of  coronavirus, and there was no other reason.