Hallo!
I did check the “upload old data” on settings both on laptop as on my phone and I am aware it would only go back 3 months - yet only results I achieved so far are error 422 & 401. When re-connecting to Strava, the old data check box disappeared on both devices.
Thanks @david - thats what I have been doing from the start, then error 422 and 401 (after refreshing) pops up - on any device/system. Shall I delete my intervals account and start over? Hoping my strava and email is not been taken yet by my current account?