I managed to solve this. I had previously generated the registry entries using this command:

regasm TheApplication.dll /regfile:TheApplication.reg

Then I had imported TheApplication.reg into the registry using regedit.

Referring to the regasm documentation here: https://learn.microsoft.com/en-us/dotnet/framework/tools/regasm-exe-assembly-registration-tool

I discovered this: "The /regfile option only emits registry entries for managed classes. This option does not emit TypeLibID or InterfaceID entries."

To get it working, I did the following:

• In the DLL project properties, checked Application ➜ Assembly Information ➜ Make assembly COM-Visible.
• In the DLL project properties, checked Signing ➜ Sign the assembly, generating a new key file.

Then I used the following command to register the DLL:

regasm TheApplication.dll /tlb:TheApplication.tlb /codebase