Following tasks could not be completely planned

Hello all,

I have a problem if I assign ressources to Meetings. If I run the planning I always get the follwing pop-up Following tasks could not be completely planned
See also the attached pic.
If I do this with an activity on the same ressources it is no problem and the planning runs fine. Also on the same day there is no other activity, etc for that ressources
So I do not know what I am missing.

Any help is very much appreciated

ok I found the issue.
I have the following structure:

Main project (administrative)
|- Subproject (administrative)
| - sub-sub-project (internal project)

I assigned my ressources to the main project, but with 0% rate.
So even if I assigned 100% to the internal sub-sub-project , it seems to be that the available rate follows that of the main project, which is zero.

If I now set the rate in the main project to 100% it is ok...
But it is also ok if I remove my ressources from the main project, so that they are only assigned to the sub-sub-project.

So long explanation but the question is now, if this behaviour is intentionally and is as follows:

Assume that
the ressource is assigned to the main project with e.g. to rate 100%, then to the sub-project 50%, then to the sub-sub-project also to 50% --> Is the maximum rate of the sub-subproject now effective 25%?
Did I get this right?

Thanky you very much