If nothing else works, you can use your main halyard to keep the mast from falling forward and detach the backstay completely. usually, the forestay with furler is more difficult to connect. Once your forestay is attached, you can pull the top of the mast backwards with the halyard (use a winch) and attach the backstay.
It may be the sequence that is causing the problem. When the mast is stepped, attach the fore stay first, then the cap shrouds and finally the backstay. This will keep the mast up right while the lowers are attached and the rig tuned properly. There should be plenty of slack in all the shrouds until all of them are connected. Trying to "perserve the rig tuning" by only taking a few turns off the turnbuckle often causes more work than it saves.Once your forestay is attached, you can pull the top of the mast backwards with the halyard (use a winch) and attach the backstay.
Is she up now? What's holding her?will look into that next time I bring her down