Waypoints in GPX files can have a symbol names attached to them, but the actual symbol is not included in the file and there isn’t a standard set of symbols, so different programs use different names and most programs can’t show the symbols of other programs.
If your GPX file was generated by Coastal Explorer, then it would use Rose Point’s symbol names and the correct symbols would show up on marks. However, Coastal Explorer on the iPad and iPhone does not currently support icons on waypoints in routes, so that could be what’s happening here too…
Also, if you are using Coastal Explorer to export a GPX file which you are then importing into Coastal Explorer, be aware that GPX is a “lowest-common-denominator” format and you might be losing information. Only the NOB format can handle all of the various navigation object types and properties that are available in Coastal Explorer.