It is often easier to cut off a piece of the hose with the connector in it, so it becomes easier to work on. Sometimes dunking the hose in hot water softens it up enough to be able to pry out the connector. Slicing the hose carefully with a sharp blade like a surgical knife also works well.

We could have used you here this afternoon as we struggled with these connectors. Any tips for how to get them on easier?

Heating the hose or adding some lubricant usually helps.

Since it is a water line, try putting the end of the line in a container of hot water, that'll kill two birds with one stone.

Petroleum jelly might work as a lubricant as well; it won't dissolve in water. But don't use it on hoses containing natural rubber, because it breaks down latex.