W10  2 PC's cannot map drives...

Office building with 4 separate offices...common router and each office on it's own subnet....
I support only 1 office...not the building...

2 PC's mapped drives to each other...they lose mapping about every 6 months or so...

Upgraded both computers to W10 Pro mid 2018...mapped drives both ways....about 6-7 months later the drive mapping was lost...got it back by deleting the mapped drives and re-mapping....been working fine until now...

Normal drive mapping process is not working...

Here is what I've done...
1.  Set static IP's on both comptuers...
      Judy PC  192.168.63.178 /24  gw 192.168.63.1
      DavePC   192.168.63.182 /24  gw 192.168.63.1
2.  Checked that C:\ drive on each computer was shared...
3.  Checked each computer has same username and pw...
4.  Successful IP mapping drive from JudyPC to DavePC...
    That mapping is working correctly...could not mapp with CN...

5.  Cannot  map from DavePC to JudyPC with IP or CN...THIS IS THE PROBLEM....
6.  At DavePC Network icon does not "see" JudyPC...
7.  Print and file sharing is on with both computers...

So I started digging and did the following...

Googling around I find mapped drives in W10 sometimes disconnect...so I ran...
net config server /autodisconnect:-1

I checked the Windows service Function Discovery Resource Publication  set it to automatic and started it...

So far....nada....

From JudyPC I can map a drive with IP to DavePC....that is working...
But I cannot map a drive from DavePC to JudyPC....AND I CANNOT PING JUDYPC  IP ADDRESS...

Appreciate any and all suggestions...