I have the same issue after the latest update on my S20 Ultra 5G. After the update, Fast Wireless Charging will not work with any of my fast chargers, but they worked before the update. Fast Wireless charging is turned on, so it's not that. Samsung needs to address this ASAP.
This stinks. I have S20 5G on T-mobile. Got update March 22. Fast charging on my Ubiolabs charger that worked for past 1.5 yrs Costco stopped working. It works with no problems on my son's S10+