Sorry that the Liquify tool in Photoshop 22.4.1 is showing a blank grey screen.
Would you mind sharing your computer's OS along with your editing workflow?
Please note that some Photoshop features have special system requirements. For example, Liquify and Oil Paint require your computer to have a compatible graphics processor (GPU) installed. Also ensure that the Performance > Preferences > Use Graphics Processor setting is enabled in Photoshop.
Further, the performance of certain features benefits from enabling the OpenCL technology.