Why can't I access Photoshop's super resolution/enhance feature?

Latest photoshop 22.3.1 enhance/super resolution feature won't work because Photoshop says my GPU needs Metal support. However, my late 2015 Retina iMac Quad core i7 is 64bit & supports Metal. Its GPU, an AMD Radeon R9 M395X, has 4GB. The iMac's System Information, under Graphics/Displays, states that Metal is supported (Metal GPUFamily macOS 2). So why can't I access Enhance in Photoshop? I'm on Big Sur 11.2.3. Thanks.