Why Both the UK and the EU are Ignoring the Good Friday Agreement

The Good Friday Agreement is meant to make Northern Ireland equally seamless both north-south (the Republic of Ireland) and east-west (the UK). 

The EU insists on the Protocol because it keeps north-south seamless. The UK objects to the Protocol because it prevents east-west from being seamless. 

Both the UK and EU are saying they're right because their view is in line with the Good Friday Agreement. But the GFA guarantees seamlessness for north-south and east-south. The UK and EU are ignoring one in preference for the other and that is strictly against the GFA. So this means both the UK and the EU are lying. 

Yes, the UK agreed to the Protocol so it should still abide by it. However, agreements get revised and ammended all the time. The EU's absolutist view of never revisiting the Protocol is uncalled for, especially after admitting it was causing problems.