There are formulas in the family which appear to restrict the allowable angles to 11.25, 22.5, 45, 90 degrees which is usual for pipe fittings. Interestingly there is not a 30 degree angle which you said you had successfuly created.
In the lookup table (attached) the valid angles are 11.25, 15, 22.5, 30, 45, 90.
So as I said earlier the manufacturer will have restricted the allowable angle values to the fittings which are commercially available.
If you really want a 60 degree elbow then you need to create new lines in the lookup table with 60 degrees as the entry in the column D, but you also then need to have applicable values for the other columns E to P on those 60 degree rows and that data is probably not available from the manufacturer if they don't actually sell that product.
Another option would be to use a generic elbow family in which the geometry is mainly driven by formulas and can flex to any angle..