Synology DSM not working on DS920+ DSM 7

All integrations worked like a charm except the “Synology DSM” integration.

I made a special account on my DS920+ DSM 7 for Home Assistant with no 2FA.
( i have read that this can cause problems )

i run Home Assistant in a docker container on the NAS mentioned above.

When i run the “Synology DSM” integration following error is posted in the logs

Logger: homeassistant.components.synology_dsm.config_flow
Source: components/synology_dsm/config_flow.py:192
Integration: Synology DSM (documentation, issues)
First occurred: 17:18:28 (1 occurrences)
Last logged: 17:18:28

{'api': None, 'code': -1, 'reason': 'Unknown', 'details': "ConnectTimeout = (<urllib3.connection.HTTPSConnection object at 0x7f1cf32c2970>, 'Connection to two.synology.me timed out. (connect timeout=30)')"}   

if i use the ddns to connect to my nas it works as intended.
do i need to open a other port on my router ?
or activate a other setting on my NAS ?
or make a firewall rule for set port ?