I finally emailed the NTA yesterday about if I should send the tamper proof discs back.
They replied today.
Following your application to NTA for the above mentioned licence to be placed into a period of suspension, NTA confirms that this SPSV vehicle licence is now suspended until 12/08/2020. The licence is being suspended as there is currently no SPSV insurance cover on this vehicle.
The suspension of licence is being facilitated under section 12(3) of the Taxi Regulation Acts 2013 and 2016. The licence will cease to have effect during this period and the period of this suspension shall not be construed as to extend the period of operation of the licence.
Under Section 17 of the Taxi Regulation Acts 2013 and 2016, whenever a SPSV licence is suspended you must do the following immediately;
Remove the roof sign from your vehicle (Taxi/Wheelchair Accessible Taxi).
Remove NTA tamper proof discs from front and rear windows of your vehicle.
Within 21 days, return NTA tamper-proof discs AND the SPSV Licence Certificate to -
National Transport Authority, SPSV Licensing Section, PO Box 436, City North Business Park, Tuam Road, Galway.
I wonder why they suspended it until 12th August? my insurance is due end of July.

as usual they have made things really simple for me.