There are spring latches at back of the cabinet for each drawer that grab the end of the drawer rails to hold them closed. The latches flip open when the drawer is opened, grab the rail and flip closed when the drawer is closed.

One of them probably somehow got flipped closed when the drawer was open and now isn't functioning properly.

Remove the lower drawer so you can get to the back of the cabinet and clip the affected latch open.

Another possibility if the the latch isn't the problem is that the link support that holds the water supply and drain hose so that they fold properly behind the drawer when it's opened and closed has broken and the hoses are interfering with the drawer.

Ah! thanks so much - can see the problem...one latch is broken and the other one the spring has come off

This helped me quite a bit. Thanks!