Decide on your idea of priorities for the various activities first. Then proceed with check in based on that.
If Palo and Remy brunch are first on your list, try to have a first choice day and second choice day ahead of time, for quicker navigation and go for those first thing.
If you are wanting to book excursions that tend to sell out (not sure what cruise you are on) like private charters or helicopter tours in Alaska, you may want to make that your first pick instead.
Tastings are also pretty popular and often sell out.
If you have any kind folks in your cruise meet group that are a higher
castaway club level than you, they may be willing to log in and have a look at what activities are still available and at what times. This can help make things a little easier.
Personally I tend to make a list on a piece of paper in order or importance, listing what day they are on and when my window opens I just go down the list in order. I always have a back up plan available too in case something I wanted wasn’t available.
Lastly it’s not uncommon for the website to give people troubles. If it happens keep trying!
Aby