I believe it is just a WARNING and can be ignored. 

I am seeing the same diagnostic - it is a Critical Diagnostic.  Can we ignore Critical Diagnostics?

I am not able to produce this diagnostic. You may be able to ignore it and e-file. https://proconnect.intuit.com/community/individual/help/diagnostic-reference-ref-frequently-asked-qu...

were you able to e-file and just ignore it?

We are still waiting for one piece of information before we can efile, so I'm not sure yet.

I am also seeing this critical diagnostic.  The trust is a CA resident complex trust return and I've noticed the diagnostic appears for me when I add an additional non-resident state to the return (Arizona).  I have not found any state specific settings that have any effect on this error, other than deleting the extra state from the return.

Anyone try to file and ignore this critical diagnostic yet and can confirm that works out?

It does appear to be a state specific critical Diagnostic, I don't know if its on any multi-state return or just ones that include certain states (like mine with Arizona).  However I was able to ignore the diagnostic and filed without incident.  All the returns have been in an "Accepted" state for several days now so it would appear to be some ignorable bug in PTO (and apparently Lacerte as well).