Rakshi...
There's no other way than restoring your phone with nad hard reset, I fear.
WA people don't care of a dead OS walking like Windows Mobile. MIcrosoft people left the OS to die, so they care even less of their customers.
I made an hard reset, but obviously I couldn't make a backup of the lastest chats.
Luckily I had my backup Android phone to use WA in the meanwhile.
I hope you did some backup of your chats, lately. Otherwise you wait it will go back working for a while, you make the backup of the chats and then proceed to the hard reset.
After the hard reset I suffered of a problem avoiding me to sign in for fast-ring updates. Only yesterday MS solved it, all of a sudden, after my complaint on the feedback hub ahahaha
It's a joke.