If things aren't working, try this...

[dmstraker]

Sometimes things just aren't working as you know they should be. Is it Affinity? Is it your computer? Possibly. But often it's a bit of missing knowledge. Here's a few checks I've picked up along the way:

 

 - Select pixel layer

 - Selection/deselect (ctrl-D) 

 - Close open boxes

 - Ensure right colour selected (eg for mask painting)

 - Layer/rasterise

 - Check opacity (of brush, layer)

 - Check layers in right place (eg adjustment layers have different effect in different place)

 - Check blend mode 

 - Check blend ranges

 - Wind back history and try last steps again

 - Ensure Affinity window selected

 - Look in help system (F1)

 - Search this forum (then post question)

 

Any more? What do you check when things don't seem to be working?

[v_kyr]

Also I would check system processes, possible huge memory or CPU usage, determining if the system maybe does perform RAM to disk and vice versa swappings etc. Further if some other task might have kicked in and halted or slowed down the overall processing, like virus scans or indexing tasks etc. - All in all there are also some other system processes which can hinder a fluid working behavior.