I'm having the same "No connection to the management station." issue on two different sites with different circumstances.  The issue has only presented, thus far, on iPadOS using Safari.

Site 1 - Desigo CC 5.1 QU 2 - Corporate issued SSL Certificate - FlexClient works from Server and PC, but fails in Safari with "No connection to the management station.".  Multiple firewalls involved, a VPN connection for the iPad to connect to the network.  Customer is able to access the Desigo CC Website, but fails to log in every time.  

Site 2 - Desigo CC 5.1 QU 2 - Self-signed SSL Certificate - FlexClient tested from Safari on iPadOS resulting in "No connection to the management station".  FlexClient works from Server, did not tested from PC, fails in Safari on iPadOS with "No connection to the management station".  A VPN connection for the iPad to connect to the correct side of the network.  Customer is able to access the Desigo CC website without issue.

Tested on an external development system using Desigo CC 5.1 QU 2 and a self-signed certificate - Accessing FlexClient with Safari on iPadOS successful with no issues. - This test was using Site 2's project as a test method - No changes were made when restoring the project.

I've checked every detail I can, but seem to be overlooking something miniscule.  Anyone with suggestions, I would greatly appreciate it.  

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Split from Desigo CC Flex Client: "no connection to management station".

Hi John,

Attach doc. you may try using the program develop for Ver.6.

Hopefuly it will work. Since work on mine.

Good Luck

Unfortunately, this did not resolve the issue for me.  I did review what this attachment was doing prior to applying the change.  Then I attempted to apply it.  It did not resolve my issue.  I'm not sure if this is a Firewall issue since the clients are connecting over VPN, if it's an issue with their Safari, or what it could be.  I'll be reaching out to Siemens Support today on it.

Thank you for your attempt to assist,

-John

AutoGen_7156385

Hi John,

Attach doc. you may try using the program develop for Ver.6.

Hopefuly it will work. Since work on mine.

Good Luck