Our Viator voucher was accepted without question and our tour on the Oslo Hop-On Hop-Off tour went very smoothly. The bus picked us up conveniently right at the cruise terminal. The earphones worked well, the commentary was clear and the pickups and dropoffs were timely. It gave us a good overview of the City and an efficient way to travel to the Vigeland Gardens with their magnificent statues beautifully displayed.
Our Viator voucher was accepted without question but 2 bus companies have apparently recently merged, making for a great deal of confusion. We got on the red bus right at the cruise terminal and then were told to switch to the green bus. We realized by the time we got to first stop at the Gefion Fountain that the green bus was going to make a much bigger loop than we had time for so we got off and got on a red bus. Whenever we asked the various drivers a question, apparently they were as confused as we were about what was going on. Our intention was to get off at Rosenborg Castle to have a picnic in the gardens but the bus whizzed right by that scheduled stop and took us back to the beginning at the Little Mermaid. So...we got on another bus to try again. This time when we got to Tivoli Gardens, the driver announced that the bus was taking a 20 minute rest! So we had our picnic on the bus while we waited for it to take off again. This time it did stop at the Castle and we enjoyed the Gardens but not the long time it took us to finally get there. The headsets often didn't work so we rarely got any commentary and when we did, loud was the only volume. We saw a lot of Copenhagen from the bus but because of the confusion, we didn't have time to spend at the stops. I would recommend finding another way to see the city.