Without knowing what that DOS program would be, nor what it is supposed to do after a menu selection, there’s no real answer.

My best guess would be that a (sub)program is to be started. Though not found since it tries to start for instance c:\dosprog\proga.exe while there’s no c:\dosprog in DOSBox. Check if the folder/drive structure and path setting are the same in DOSBox and the virtual W10. If it’s all local, copy c:\dosprog for instance to c:\DOSBox\dosprog, and MOUNT C: C:\DOSBox.

The program is something that was made for said company.
The folder structure is like this
NAMEOFPROGRAM\SOMEOTHERNAME\allfileshere
Inside the folder I was given are a bunch of .exe's, 1 install .bat file and office files that have no real use afaik.

As for the structure, it's the same in W10 as on my local pc.
C:\NAMEOFPROGRAM\SOMEOTHERNAME\

What I mount is: "mount C C:\NAMEOFPROGRAM\SOMEOTHERNAME"
This is the exact same directory as wel.

I'm doing exactly the same thing, the only difference is that it works on the virtual w10 but not on my local pc through dosbox. The install bat is of no use btw, never ran it on the virtual w10 and it works there.

1st DOSBox is for DOS programs not "Command Prompt" programs. So if the program\batch doesn't work in DOS but only in Windows then it's not a DOSBox problem.
2nd If you do a "Mount c c:\dir\dir" then c:\dir\dir becomes the root of c:\ which causes issues with some DOS programs. Create a new folder for your program and mount that root folder as your c:
3rd DOSBox doesn't support Long File Names inside the guest.
4th Don't expect much DOSBox support if you're not trying to run a game in DOSBox unless you're prepared to pay in advance for support.

1. It's not a command prompt program, It's DOS.
2. The names used aren't long, hey're around 7 chars.

To be clear, it works on the virtual w10 32-bit; but it can't be run on a 64-bit windows.

Note that DOSBox is intended for games, not programs. It is missing features that many programs need that are not required for games, such as support for share. A better option would be vDosPlus or a VM with real DOS installed in it.

With "mount C C:\NAMEOFPROGRAM\SOMEOTHERNAME", the DOSBox C drive has no NAMEOFPROGRAM directory.
So copy C:\NAMEOFPROGRAM to C:\DOSBox. Then MOUNT C C:\DOSBox, so there’s actually a C:\NAMEOFPROGRAM\SOMEOTHERNAME in DOSBox.

collector wrote:

Note that DOSBox is intended for games, not programs. It is missing features that many programs need that are not required for games, such as support for share. A better option would be vDosPlus or a VM with real DOS installed in it.

This is likely to be your best and only solution for running native dos software without being able to share the software with us to figure out what's going wrong. DOSbox users are looking to play games. Look up how to install MS-DOS 6.22 in virtualbox if vdosplus doesn't work out.

If you get it working, it's very easy to export the virtual machine and import it into your clients machine later.