We had exactly this problem. Tray was out and could not be fitted back in because for unknown reason, the infuser was right next to the bottom of the machine leaving no space at all to fit the drip tray back in.
We solved it by simply pushing the coffee waste disposal unit back in WITHOUT the drip tray. We closed the door of the machine and it reset itself, believing all parts to be in place - the machine moved the infuser up to its normal position and we could fit the drip tray once more.
Jonas, February 2020