RDM unable to connect via SSH to Cisco and Huawei switches

I have 3 switches in a LAN segment and my PC also has an interface in that segment. I can connect successfully only one of the switches - a HPE Procurve. The other two (a Cisco Catalyst 2960X and a Huawei Cloud Engine S6730) give me this error:



The "Check Is Online" tool reports success, for all switches:



and I'm able to connect to all switches using PuTTY from the same PC.

I attempted to change IP address of the Huawei's switch entry with the IP of the HP entry (which works) in order to check if there is something wrong with the connection entry itself , but there isn't - the entry works with the HP's address. I tried some other Cisco switches from Catalyst and SG series with no luck.

Regards
George