Error variables must start with a "?"

[InesaDiamond]

I've tried to run this on my own pddl files, and files I've found online. I've also looked through the PDDL files and the variables definitely do start with a ?. How do I fix this?

[maltehelmert]

Can you share an example pair of PDDL files (domain + problem) for which the error occurs?

[maltehelmert]

Closing this because we didn't get a reply. Feel free to open again if you are still affected by this -- in this case please show us an example that we can use to reproduce.