If you suspect that your retractable hose reel is jammed, it may be due to a loop of hose not feeding correctly or hose the folding on itself.
In the photo below, you can see there's been a loop which hasn't fed correctly:
This requires manual correction. To begin pull the hose out as far as it will currently allow, then inspect the hose on the barrel (lift the flap lid and have a look inside the reel case) to see if you can see the issue clearly.
It's very important that you do not reach into the case - keep your hands very clear of all mechanisms at all times. If you cannot see the fold/issue which is causing the hose to be stuck then please do not proceed.
If it is clear and visible (i.e you can see a fold or another issue) and providing the hose is locked in position (and not between locking points), then you can attempt to correct the hose.
You should be able to feed a small part of the hose back into the case, and using the viewing window you'll be able to roll the hose (if needed) and get some slack on that section of the loop which will allow you to correct the hose.
Once you've been able to correct the direction of the hose, the reel should allow the rest to be unfurled to the "end of hose" marker - once this has been done you can retract the hose, and supervise the retraction to ensure the hose is rolled back in the case correctly.