Immobilizer light stuck on after battery swap, am I screwed?

Swapped the battery in my Patrol last week and ever since then the immobilizer light just stays on and the car cranks but won’t fire. Classic me thinking it would be a five minute job. I’ve tried the whole lock and unlock reset trick with the fob, disconnected the battery again, left it overnight, nothing. Someone in a WhatsApp group mentioned I should look into reliable key programming and immobilizer reset in Abu Dhabi rather than letting the recovery guys drag it to a dealer where they’ll probably charge me half a month’s salary. Honestly I didn’t even know this kind of workshop existed until now. Before I call anyone though, is there a chance I’ve permanently bricked something or is this a pretty routine fix for a proper technician? Also curious how long something like this usually takes because I need the car for work by Sunday. Any advice appreciated, feeling pretty dumb about the whole thing.