mpro

Hello, I downloaded the Affinity Photo on my MacBook Air and I am unable to use the tools on the left (all the brush tools, erase tools, fill tools, etc.) I cannot repeat what the tutorials show. It seems that the tools do not respond to mouse clicks, even though I can use all the other functions from the top menu (layers, etc.) with no problem. Could you please assist me in resolving this issue. Thank you, Margarita