Failed print, curling on calibration Prusa Mk3S

[Bobslay]

Hi,

I am struggling to get any successful prints ( it was hit and miss before, now is 90% fail). I have attached the calibration square and you can see it curls a huge amount. I've also shown a print which fails on first layer. I have a Prusa Mk3S. I have tried two different PLAs and the same exact effect.

Any thoughts what might be causing the curling?

Thanks