Person right above you had the same issue here was my response to them:
If it's complaining about HTTP then there there might be an issue with your AppDynamicsConfig.json. Can you vi back into it and make sure you set it to point to the Controller correctly?
This doc may help: https://docs.appdynamics.com/display/PRO45/.NET+Agent+for+Linux+Advanced+Configuration+Options
Pay special attention to the ports you're using also to make sure they're not blocked, and that you're using the correct ones whether you're using SSL or not. Another place to check would be the cert trust.
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