If it was a bedding fuchsia (non hardy) it should not have been planted outside till end of May at the earliest, they're frost sensitive. If a hardy bush fuchsia, did it need hardening off before planting out (if inside when you bought it, or under shelter)? The shock of the cold could cause this, otherwise, did you water it regularly.

Possibly vine weevils? Are there white C-shaped grubs with orange heads in the soil where the roots ought to be? They eat roots of fuchsias & begonias over winter.

Did you heel it in enough? They need the soil to be pushed down fairly firmly around the roots, and watered well even if it rains.