Bluetooth Won’t Connect

So it seems that my iPhone (8+) can’t detect any bluetooth devices, let alone connecting.

I tried turned it off and on again, even resetting my iphone, but it still won’t connect to any of my bluetooth speakers.

My sister’s macbook could find them tho, so it’s likely the speakers aren’t at fault.

Also, I tried to use airdrop to send pictures to my sis’ iphone and it’s still working.

My iPhone just has this issue to find another bluetooth devices, i think.

Any idea what really happens, and what I should do?

Thanks in advance!