I’m currently dealing with the same issue. My bunnies would rather taunt each other than get their exercise in during their out time, so I’ve been getting creative. Here are some things I’ve done:
Try a new game. Once you’ve got your bunny’s attention, try a little game that you think your bunny might like. My rabbit loves to knock things over and generally cause havoc, so we have started to play a stack-and-topple game with toilet paper tubes. It’s enough to get him in a playing mood, and he usually decides to go find something to do afterward.
How about a new and interesting toy? For mine, just some normal toy wasn’t enough to get their interest. I discovered by accident that the new bunny loves to run through tunnels, so I built a long one against one wall just by leaning some cardboard on it. That got her moving! If you’ve got a climber, you can try building a “maze.” I end up taking a few cardboard boxes, cutting out doors and windows, and stacking them for the exploring rabbit. They’ve got a pre-made thing like it in the store.
Do they have a favorite toy? As a final incentive to get my buns out and about, I only give them their treat ball during outside time. Often, I don’t even fill it. They’ll spend untold time rolling and tossing it, hoping for something to come out. Adding a little hay inside will make it harder for the treats to fall out without making too much of a mess, thus lessening the amount of treats you need. This one gets ’em every time.
Best of luck!