First, I saw what User 'VistaLover' suggested (uBlock Origin = UBO) to you, and I agree strongly with that.
But, IF you are insistent on using ADBLOCK PLUS, this could help you (or not).
Under NM28 Browser MENU, choose VIEW, then point at TOOLBARS, and Click on CUSTOMIZE. The CUSTOMIZE 'box' should open, with some ICONS that you can choose to (Mouse) DRAG them up onto the Browser MENU area (next to the URL ADDRESS input box, on the right side). So, the ADBLOCK PLUS Icon MIGHT be 'mixed in' there, inside that CUSTOMIZE 'box' somewhere. And if so, just DRAG that ABP Icon up next to OTHER Extension Icons that you likely already have them there visible on NM28 Browser. Reason that I suggest this, is that I had this 'Hidden Icon' situation happen (UBO Icon ended up in CUSTOMIZE 'box') with my install of UBO Extension on the BASILISK55 Browser (also a ROYTAM maintained one).
Anyway, regardless, does not hurt to suggest checking in the (NM28 Menu: VIEW ; TOOLBARS) CUSTOMIZE 'box' for a 'missing' EXTENSION Icon from a seemingly otherwise successful EXTENSION install.