Hey lads and ladies,
The health kit on C1 will not open for me at all. If comes up with a message saying 'no error message found' Any ideas?

This is happening to me, too.

I'm guessing you're both on Windows 10.

To whatever end, having a read of these useful resources.

Are you running the game as an administrator?

This still has not been fixed as of April 2019.

I have this problem too, running as administrator doesn't help

Same problem here! :( Very frustrating.

SAme here on win 10 but all solution didn't worked till I treid this:
Do the following change the filename of "Health Kit.exe" to "HealthKit.exe"
then go and find the file name Applets in the same directory (the c1 default directory where also the health kit file is)
Open it with notepad(++) or any other simple texteditor, change in it the word Health Kit to just one word HealthKit, save and close.
Now launch c1 and your healthkit is again working in full glory!