The Angels created the better openings and will rue their inability to convert.
On 22 minutes, skipper Jordon Thompson forced a low save from towering Magpies keeper Jordi Van Stappershoef. Eight minutes later Tom Leahy struck the base of the post with a left-footed effort that rebounded kindly for the visitors.
Ricky Korboa had a golden chance after being played in by Frankie Baker but blazed over when Leahy was well placed for a square pass.
After the break, Tonbridge stepped up the intensity. Korboa weaved into the box on 51 minutes only to be denied again, while Baker saw an effort deflect onto the post following a defensive mix-up that briefly left the Maidenhead goal exposed.
Leahy also saw a glorious late opportunity from six yards superbly saved - a moment that felt decisive even before the final twist.