Cant see computers on network shares

I have 3 computers on the network. All have shared folders . My problem is as follows.

Lets call the computers c2, c3, c4. I am using network shares

When on computer c4 , computers c2 and c3 are not listed at all under network. Sometimes I do see c3 listed but cannot access it.

In computers c2 and c3 , all computers are listed and I can view all the shared folders in c2 , c3 including those on C4.

I cant understand why c4 have such problems viewing other computers on the network. I have rebooted router ( E4200) and computers but still have same problem .

All shared folders are properly shared. and no passwords are required for networks in adv sharing .

Not sure how to proceed to fix problem . Please advise Tks

I solved the network shares sproblem by first connecting all the computers to a homegroup . Then network shares also worked. I dont know why.

After leaving the homegroup for all my computers , a phantom homegroup was left on c2 so I could not create a new one nor can I join the phantom homegroup from c3 and c4 . I did a quick search and found that I have to shut down all computers then start any computer that does not have the phantom homegroup to create a new homegroup. Apparently one can create new homegroup with impunity after all computers and shut down and only turn on one of them to create a new homegroup !