Bonus almost 2 years overdue?

To get the bonus paid, your contract and bonus addendum must be uploaded to GIMS.
Your Unit, your state, Camp Robinson and NGB all have to review it.
Once all of that is done, and payment is due (or overdue) then your unit, State, Camp Robinson and NGB all have to approve payment.
The most common fail is the unit RNCO not opening the Unit Bonus Eligibility Report, opening a case and clicking on Eligible.

Your RNCO might be saying he doesn't need the paperwork because it was already uploaded.
Just to be sure, sit down with him, have him open your bonus case on GIMS, open the Documents tab and show you that the required documents are uploaded, and then open the History tab to show what step your bonus payment is pending at right now.

If your RNCO is unable to open GIMS because he doesn't have access or doesn't know how, then you need to talk to your Commander immediately.

You do realize there is paperwork that needs to be turned in, most units it falls on the Soldier to turn that in.

Ok, first things first... pull your contract and make sure that you have a 20k bonus listed on there. If you do not then you will not get one and there is nothing you can do about it sadly. Once you have verified that it is on your contract, take that to your readiness NCO and press. Give him or her a short period of time and then take it further up the chain.