A common cause is a clog. Which can be caused as water freezes in the line, or if the ice machine’s filter itself is clogged. If the filter is clogged, then it can be replaced or fixed quite easily. (And the filter should be replaced every 6 months anyway.)
Some clogs can be fixed by shutting the ice machine off for a bit and allowing for the frozen water to melt. But not all clogs are caused by frozen water. If you think you are dealing with a clog that is not the result of frozen water, or are unsure about the problem in general, consult a professional for help.