Second monitor connected to my iMac won't turn on.

I have 2nd monitor connected via sitecom "CN-393v1.001 USB-C Multiport Adapter + PD".

For some reason after sleep mode the second monitor won't turn on.

there is no messages that there is no signal or some thing like that.

problem is not permanent, from time to time it's working fine.

the only solution right now is to disconnect the whole adapter from Mac and reconnect it.

external HDD connected to the same adapter working with no problems.

[Re-Titled by Moderator]