Unable to Transfer Files between Computers

The problem is that the 3D printer has an internal PC running Windows Embedded. What we need to do is transfer files to that computer (printing is not a problem). We can Remote connect to it but the Master PC (Windows 10) cannot see the other computer. Therefore we cannot do file sharing with it.

Saying that I am trying to connect to a printer was probably giving you too much information. This is essentially attempting to network two PCs, regardless of the existence of the printer.

Our only other solution is to shut down the printer, pull out its IDE harddrive, put it into an external enclosure that has USB, and then simply attach that to our main computer and transfer directly. Then put the HD back into the printer. A bit of a pain, especially when mstsc.exe connects just fine to the printer's computer, but Windows networking cannot.

For file sharing, the 2 PC's have to be in the same workgroup. What workgroup is defined in that PC inside the printer? Once you know that, change it in your PC to be the same.

Excellent point! How do you find the workgroup name through the command prompt? If I do "net config rdr", I get the Workstation Domain Name and Logon Domain Name.

Can you FTP the files over like many small computers do today?

I suppose that might be possible if the printer were on a network that had access to the Internet. We have it dedicated to an ethernet connection on its own network.

Was done without the Internet for decades. I worry here many are forgetting the old ways.

...left scratching my head on the post. Kees had best answer, but to add to it, I think the OP would also have to share the printer also in that workgroup?

Not sure, since again, it is simply one PC talking to another. The printer is kind of like a side gig.

if you want anyone in the "workgroup" to have access to it also. You should be able to right clk on the printer link and get an option to "share" it. It can be open or password required sharing.

Yes, the connection between the two is via Ethernet (CAT5). We can remote connect to the computer via the standard system32/mstsc.exe, but Windows does not see anything as far as a connected device. Might be the workgroup name advice.