Install AirNotifier v3.0
Have tried on Ubuntu twice and CentOs7 once (same issues on all 3 servers).

Restart AirNotifier

Make test call (using push service to send APNs).

Log print below received.

1602660704 E [MainThread][root][push.py:153] no active apns connection
1602660704 E [MainThread][root][push.py:177] Traceback (most recent call last):
File "/root/airnotifier/api/push.py", line 174, in post
self.send_response(ACCEPTED)
File "/root/airnotifier/api/init.py", line 212, in send_response
self.finish(data)
File "/root/airnotifier/api/init.py", line 215, in finish
super(APIBaseHandler, self).finish(chunk)
File "/root/.local/share/virtualenvs/airnotifier--hHQdAqd/lib64/python3.6/site-packages/tornado/web.py", line 1119, in finish
raise RuntimeError("finish() called twice")
RuntimeError: finish() called twice
finish() called twice
1602660704 E [MainThread][tornado.application][web.py:1788] Uncaught exception POST /api/v2/push (<IP_ADDRESS>)
HTTPServerRequest(protocol='http', host='<IP_ADDRESS>:8801', method='POST', uri='/api/v2/push', version='HTTP/1.1', remote_ip='<IP_ADDRESS>')
Traceback (most recent call last):
File "/root/airnotifier/api/push.py", line 174, in post
self.send_response(ACCEPTED)
File "/root/airnotifier/api/init.py", line 212, in send_response
self.finish(data)
File "/root/airnotifier/api/init.py", line 215, in finish
super(APIBaseHandler, self).finish(chunk)
File "/root/.local/share/virtualenvs/airnotifier--hHQdAqd/lib64/python3.6/site-packages/tornado/web.py", line 1119, in finish
raise RuntimeError("finish() called twice")
RuntimeError: finish() called twice

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/root/.local/share/virtualenvs/airnotifier--hHQdAqd/lib64/python3.6/site-packages/tornado/web.py", line 1699, in _execute
result = await result
File "/root/airnotifier/api/push.py", line 178, in post
self.send_response(INTERNAL_SERVER_ERROR, dict(error=str(ex)))
File "/root/airnotifier/api/init.py", line 212, in send_response
self.finish(data)
File "/root/airnotifier/api/init.py", line 215, in finish
super(APIBaseHandler, self).finish(chunk)
File "/root/.local/share/virtualenvs/airnotifier--hHQdAqd/lib64/python3.6/site-packages/tornado/web.py", line 1119, in finish
raise RuntimeError("finish() called twice")
RuntimeError: finish() called twice

Access front end UI.

Go to 'voipexprod'.
Go to APNs configuration.

Remove the last character from any field.
Save.
Add character back to the field.
Save.

1602660712 I [MainThread][tornado.access][web.py:2246] 302 POST /applications/voipexprod/settings (<IP_ADDRESS>) 8.88ms
1602660712 I [MainThread][tornado.access][web.py:2246] 200 GET /applications/voipexprod/settings (<IP_ADDRESS>) 25.53ms
1602660715 I [MainThread][tornado.access][web.py:2246] 302 POST /applications/voipexprod/settings (<IP_ADDRESS>) 7.66ms
1602660715 I [MainThread][tornado.access][web.py:2246] 200 GET /applications/voipexprod/settings (<IP_ADDRESS>) 25.30ms

Make call and it works.

1602660721 I [MainThread][root][dao.py:25] find token: (<TOKEN_ID>)
1602660721 I [MainThread][root][push.py:111] sending notification to ios: (<TOKEN_ID>)
1602660722 I [MainThread][tornado.access][web.py:2246] 202 POST /api/v2/push (<IP_ADDRESS>) 922.25ms
1602660722 I [MainThread][root][init.py:218] PushHandler call ends 0.9223105907440186

1. When a rest call is made in to the service, immediately after restart, it does not work (with correct configuration).
2. Why does it take a visit to the UI to hit save to restart the connection?

Currently this activity is having to be undertaken daily to keep the service usable.

NOTE:
This issue occurs after a "104 Connection Reset by Peer" as well and requires the same change/save in the UI to make work.

Would it be possible to have a look at the above and see whether there is a resolution?
Happy to supply any additional information if required.