FTP test fails

Hi all,

yesterday I tried to perform FTP test with my Edge 830 for the first time.

My current determined FTP from Garmin is 208 W (should be quite a bit higher).

First I started with 20 minutes with very easy cycling, then realized that I have to push lap button to start with the core FTP test.

Then first block was 215 W for 4 minutes, followed by 235, 260, 280 and ultimately 305 for 3 minutes.

After short 3 minute cool down periode, I received message that FTP could not be calculated based on the training. Please try again.

That is quite frustrating... seems that the FTP test is not realiable.

And there is also no way to repeat it the same day as it was exhausting. Anybody who has experienced the same?

That's the link to my activity: https://connect.garmin.com/modern/activity/4263345922

Did I anything wrong?