You won’t find an electrician that has good things to say about gfi receptacles - they are the weakest link in residential wiring.
First go down your breakers and turn each one off then back on. Not all tripped breakers look tripped. Get one of those outlet testers and plug it in each outlet outside and inside on common walls shared with the outside plugs. It might give some useful information, or it might not.
I‘d pull the panel cover and check that voltage is making it out of each breaker - a non contact tester makes this a quick test.
Then, If you pull the cover off each receptacle there are two terminals for line power going in, and two for a load going out to another receptacle (if any). My money is on a loose connection on the furthest upstream outlet, or it’s defective.
Electricians are creatures of the least possible amount of effort, so the dead outlet closest to your panel will almost certainly be the one to start with. If there is power going into that outlet, you found the problem. If there isn’t power, but the power is fed through a connection with a wire it in the box, twist the wire nut to tighten and pull on the wires to make sure they are being held properly. If you now have power you found the problem.
If there is no power reaching the box the outlet is in, look to the inside of the wall - chances are the exterior outlet is fed from one of the interior outlets that’s closest. Pull the cover plate and check the wires for voltage - if the wires have voltage and it’s a bad connection going into the receptacle, you found the problem. If not, check any wire nutted connections in the box, tighten them and check for power. That outlet is probably fed from another outlet in the same room.
Depending on the age and local customs, if someone didn’t know what they were doing and replaced a half switched receptacle with constant power and connected power going out of that box with switched power, your exterior outlets could be attached to an interior light switch.
It would be quite unusual for outlets outside of your unit to be fed from another unit, because it violates the principle of least effort and least wire possible.
A good wire tracer would pinpoint the breaker that feeds the dead outlet, but many electricians don’t believe in them.
Good luck.
