This looks like a bug in Panorama. You've entered an isotope modification ("Heavy") with two amino acids (K and R) as the targets. Panorama is expecting only one amino acid and that is why you are seeing the error. We will need to fix this to allow for more than one amino acid target for an isotope modification.
In the mean time, instead of using the custom "Heavy" isotope modification you could use the Unimod modifications already available in Skyline. When you add a new modification, click the arrow next to the "Name" field, in the "Edit Isotope Modification" dialog to see a list of the available modifications. The two corresponding to your "Heavy" modification are:
Label:13C(6)15N(2) (C-term K)
Label:13C(6)15N(4) (C-term R)
Using these two modifications should fix the Panorama upload problem.