Message: [App Center] Unable to obtain the latest app update information online.

[zukers]

Hi,
after installing new firewall on my network I get from QNAP such errors:
"Message: [App Center] Unable to obtain the latest app update information online."
I just mention that I get information about new firmware available.
So I have opened access from qnap server to site *.qnap.com and with ports HTTPS and HTTP but I still getting these messages. This problem is for sure related to firewall but don't know which site I should allow more on firewall.
Could anyone help me?