Smoke alarm help.

[NailsHairNipsHeels]

I'm stumped 🤷🏻‍♀️

One of my smoke alarms was beeping, I assumed low battery so changed the batteries. Initially still beeping but google advised to press and hold the test button which stopped the beeping until 0330 when I started back up.
Any ideas how to fix this?
It's interlinked smoke alarms approx 7yrs old of that makes any difference at all

Are you sure it's the same one beeping? I once could not work out why mine kept beeping after changing the batteries but eventually discovered it was the carbon monoxide monitor in the same room that was actually beeping.

It's definitely the same one it's the top landing and no other devices nearby.
The others on the house are fine and sound when I press the test buttons. This one also has a wee red flashing light when beeping. When the beeping stopped temporarily it was a solid green light

If a replacement battery hasn't fixed it then your next options are to give it a hoover to make sure it's not full of dust and if that doesn't work you can buy a replacement head. They have a shelf life of about 10 years before they need replacing. You should find a serial number/ make and model on the head piece that you detached to put in the new battery. Google that and you'll be able to buy a new one.