I noticed that Bitdefender Total Security's Firewall was blocking my access to all Mapped Network Drives, which I was accessing through a Cisco Any Connect VPN.
Since I had this issue with the firewall before, I double checked the security settings in Bitdefender > Firewall and made sure that the Cisco VPN were not blocked. This was not the case. My settings of the "Ethernet 2" (which seems to be the Network Connector name in Bitdefender for the VPN) was also set to "Home" to allow more liberal access. Nothing seemed to work (also remove "Stealth Mode" and the like.
I noticed that I received "System blocked" messages still, and added a rule to allow access to the kernel .exe system file. This also did not resolve the problem.
So for me - the only workaround so far has been to disable the Firewall and use another one temporally instead. HOWEVER, this is not a solution and a pretty uncomfortable workaround at best.
I saw from previous posts over the years that I'm by far not the only one with this problem, but none of the proposed solutions there seem to work for me. Has anybody experienced something similar and has advice?