I had my watch off for a few days and went to use it again and could not pair it through the app at all and the app repeatedly froze. I tried reinstalling,clearing the cache several times with no luck
There are a couple options you can try. First would be repairing the watch to the phone, it might have somehow "forgotten" the phone it had been paired with. From your Watch Settings>General>Transfer watch to new phone. The other option is to factory reset the watch, set it up like new, then restore from backup.
