@gawjuspops
Do you have another unactivated giffgaff sim card?
Could you try these steps
(wait a few minutes between each step, wait to see if a connection symbol appears then Tey a connection)
Switch your phone off and remove the sim
Wipe the sim contacts with a cloth
Wait 5 minutes
And replace,
Select giffgaff in the pop up networks list,
(mention if you don't see a pop up list)
If you don't see a connection symbol after a few minutes
Try and select a different network mode and then a manual roam
Go to
Settings
Connections
Mobile networks
Network mode
And select one by one to see if a connection symbol appears
Go to network operators
Make a manual search and select a network other than o2
Wait till it fails then select o2
If a connection symbol doesn't appear, try an automatic selection
