When you have line loads or any members with gravity loads applied (or self-weight) that fall outside of the boundary of the diaphragm slab edge you will get the following type of warning:
---------------------------Some Gravity Load has been detected on one or more stories that is not associated with any diaphragms.It will be ignored in Notional Loads unless it is combined with one or more diaphragms. See the Loads - Gravity for Notional command.
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Under Loads - Gravity Loads you can evaluate the total diaphragm dead and live loads for each level, each diaphragm. For levels with a "None" entry, you can combine these values with some near diaphragm, override with "User Specified Values" or choose to ignore them by doing nothing and leaving the "Combine To" field set to None.
A similar error message also occurs when the masses for things outside of the slab edge are uncombined. See RAMSS Seismic Loads [FAQ] for details.