Q&A plugin: Questions is missing on Menu + a constant notification "visitor role cannot be


I have installed the plugin & translated to Hebrew with WPML.
On a subdomain I have constant message:

[Q&A] Visitor role cannot be found. Try to deactivate and reactivate the plugin, if you continue to see this message, consult our Help and Support.

I also don't have Questions on my menu not on the domain & not on the sub-domain.
I do have on both, the option to add question via upper menu New>>Question

Thanks for helping.