Unable to join Homegroup on new Inspiron 15 5559

 I've had a homegroup set up for a good while on 3 desktops and an old lap, but my brand new Dell laptop Inspiron 15 5559 with Windows 10 is unable to join.  I get to the point of having put in the correct password and clicking NEXT, then the bar just keeps on moving left to right for several minutes, then stops without any message and not joining.

 Here're the details.  One desktop (a Dell Inspiron 630 with Windows 7 Pro), one old HP desktop with Windows 10 Pro, one old home built desktop with Windows 10 Pro (all 64 bit), and an old Toshiba laptop with 64 bit Windows 7 Home.  All these join the homegroup just fine.  In addition to the homegroup, I have file & printer sharing turned on with all 4 of these.  On the Dell desktop I have 9 shared folders and two shared printers.  The new Dell laptop can access the shared folders, it's just unable to join the homegroup.  I set up the homegroup because I was having problems accessing the 2 shared printers (a Canon IP1600 inkjet and a Samsung ML-2525 laser) with Windows 10, in case you were wondering why I didn't just go with file & printer sharing instead of homegroup.

 Anyway the bottom line is that everything on this new Dell laptop is working great except that I can't join the homegroup, and I'm very curious to know why not.  I've done full virus scans with Defender and Norton 360 and have done two scans with MalwareBytes, but no malware has been found.  I also ran "SFC /SCANNOW" and it didn't find any problems either.  I've triple checked to be certain I put in the right security key for homegroup, and at this point I'm out of ideas.  Please don't suggest restoring to factory settings because I've had this problem since the first day I had this laptop out of the box before I did any customization. FWIW I'm no computer novice.

What do you suggest?  TIA