Repairing a caravan window is a tricky business as the acrylic is now aged and brittle, so great care must be taken when trying it.
A number of people have had some success with Bondrite , but again, great care in application is required and careful preparation is essential.
This is made even more difficult as the top of he window is held by a pressed on hinge bar, so the two panes are not entirely separate.
The company called EECO will effect a rebonding repair but the window needs to be sent to them (they collect and deliver), but only if there has not been a previous repair attempt.
https://eeco-ltd.co.uk/
May be worth a phone call to them.