What cws is (rightly) suggesting is that the airline has reasonable grounds when the reason why it is denying you boarding is that you do not have a recent negative covid test to show that you are not covid-infected whilst the airline has decided that this was part of its covid infection-prevention measures, and an entirely reasonable measure at that, regardless of whether it is mandated by regulation or part of the airline's own covid prevention initiative.

You will almost certainly be wasting your time trying to seek GV261/2004 compensation. What I would do in your case if you cannot have the test results confirmed in time is use the measure to ask TP to allow you to move your ticket to a different date for free. I think that would be a reasonable adjustment; asking for financial compensation simply is not.