Can't update my schematic to PCB layout in Altium
Altium Designer is similar to, for example, Microsoft Visual Studio and other major development applications, in the sense that you can open a single document or an entire project (collection of related documents).

When you have just a PCB or schematic document open, Altium has no context for updating one from the other. If you have the project open &mdash; even if you only have one schematic within it actually open &mdash; then Altium 'knows' which PCB you want to update.

The file extensions of interest (per Altium 19) are:


PrjPcb = The entire project
PcbDoc = PCB
SchDoc = Schematic


(It may help to have file extensions shown.)