Attempting to reserve 1st class tickets from:

July 4th 13:42 - Frankfort Airport to Amsterdam Centraal (ICE124)

July 6th 12:38 - Amsterdam Centraal to Cologne (ICE 125) 

July 7th 08:16 - Cologne to Berlin (ICE 824 & ICE 545)

July 9th 13:15 - Berlin to Prague (EC175)

July 11th 11:56 - Prague to Vienna (RJ79)

July 13th 09:02 - Vienna to Salzburg (RJ596)

July 15th 10:56 - Salzburg to Munich (EC262)

July 17th 09:55 - Munich to Nuremburg (ICE800)

July 18th 14:34 - Nuremburg to Frankfort (ICE624)

I have purchased a Global Pass and yet have been unable to make and pay for the reservations listed above.  The Proceed to Payment button is grayed out and will not respond.  What do I do now, wait until I arrive and take my chances to make reservations at the station?  The app is poorly written and unintuitive if one can’t make reservations and not tell you why.