Problems converting uVision project to csolution

I have a uVision (V5.41) project with over 20 targets, all using armclang v6. When I try to export the project (save to csolution format) the build output shows the following:

0 out of 0 target(s) converted
Error: 0 error(s), 50 warning(s):

I get the following warning for each target (I have substituted the target name with <target>):

Warnings:
The target "<target>" is configured with following user commands which should be run manually:
Before Build/Rebuild
.\pre-build.bat @L
After Build/Rebuild
.\post-build.bat @L "!L"

I also get warnings about re source files "not matched", ,which is because they are auto-generated by the above .bat files.

Why do I get "0 out of 0 target(s) converted" but no errors?

Thanks