If your payment plan has not yet been approved, send in a payment before the due date of the return with the voucher. It can take up to 30 days for the IRS to accept your plan, and the IRS will not honor the agreement if the 1st installment is not received by 4/18/17.

You can also pay on the IRS website directly. https://www.irs.gov/payments

Note: Your tax return may be accepted in 24-48 hours. This not the same as having your installment plan accepted. 

But in this answer from link below it is stated the opposite  information regarding your "note":
https://ttlc.intuit.com/community/taxes/discussion/how-do-i-know-if-my-installment-payment-plan-was-...
"If Form 9465- Installment Agreement Request was filed with your return and your return was accepted, you can consider the payment plan as received"
Who is right?
I have the totally same situation as topicstarter.
I filed taxes 2 weeks ago(with TurboTax) with requesting installment plan.But I still don't see any updates in my IRS account(I see only my old 2018 return).
Does that mean my return was not yet processed?
When it will be processed will I be able to see in my IRS account whether installment plan accepted or not?(it should be faster to know then wait mail notice).
What should I do if it will not be accepted? Take the loan to payoff tax debt? or any other options?