Select the PNG file you brought into your drawing and on the Properties palette, under the Misc heading, change Background Transparency from "No" to "Yes".
Work: AutoCAD 2022.1.3, Windows 10 Pro v22H2 64-bit, Intel Core i7-8700K, 32GB RAM, Samsung 960 Pro SSD, AMD Radeon Pro WX 5100, 3 Dell Monitors (3840x2160)
Home: AutoCAD 2022.1.3, Windows 10 Pro v22H2 64-bit, Intel Core i7-11700, 64GB RAM, Samsung 980 Pro SSD, NVIDIA Quadro P2200, Dell Monitor (3840x2160)