I had a similar problem with the actual heated bed bowing upwards in the middle, holding a known metal straight edge on the bed confirmed this.
The bed was replaced under warranty, but I used the aluminium foil method until I got the replacement bed.

Can only suggest to try the bed leveling STL file but increase the 'Z' offset initially to clear the high point and observe the first layer.
Perhaps start at +0.02mm offset to start and increase it in 0.01 increments until you clear the high point and shim the low points a layer of tape at a time until the different points look to have a similar amount of squish.

It is a time consuming operation unfortunately.

'Teaching Tech' on Youtube has some good videos about first layers.