Some SID's are considered Radar Vector SIDs. This means that the SID has no defined route structure, but is predicated on ATC Radar Vectors. SIDs that are Radar Vector SIDs are not able to be filed through ForeFlight and are also not accepted by ATC.
It is best to just file your intended route without such a SID and you will typically get vectors to your first fix if the fix is listed on the SID.
Below is an error message you might see if you try to file a Radar Vector SID:
"Procedure is only assignable by ATC. Please remove it from your route and re-file."