my instant chat is not working.how can i make it correct?

HOW DO I IM?
First, you must have YOUR 'Instant Messaging'
turned ON:
http://mingle2.com/user/enable_im
(Or >>My Account>>Settings>>Turn ON IM)

Then you would go to the profile of the person
with whom you wish to chat.

Under their picture there is an orange button
'Instant Message' which you would click on and
the request to Instant Message is sent.

If there is no orange button labeled 'Instant
Message' it could mean one of two things.

The person does NOT have 'Instant Messaging'
turned ON.
(In which case you could email them and request
they turn it ON.)

Or, the person is in 'Stealth Mode.'
http://mingle2.com/user/toggle_stealth_mode

NOTE: The mobile site has NO Instant Messenger.

I have got the same problem...it was fine until yesterday...followed all the above mentioned steps..but still not fixed

It is an issue, they are working on fixing it.