I have had this issue for 4-6 months. Talking on the phone to a rep was of little use as they are non-technical. I asked if I could get their IT support as this obviously was something related to my profile and their system as the error only occurs if I am logged but was told there was no option for this and was told to email customer relations who did not reply to my email.
I had the problem with the blank excursion page. It may be related to your first problem, its just really slow. Try again and give it 45 seconds, it may populate with options. It did for me
On the website go to your cruise booking in the planner and go to Payments. At the bottom in the Credits section it will show any credits for that cruise and whether they are refundable.