Typically I enjoy using Altium at work for schematic capture and PCB layout, but occaisionally it'll give me some problems when I try to synchronize my PCB file with my schematic. When syncing, I'll get a lot of error messages about unmatched nets and failures when matching unique identifiers. In the past I'd try my best to backtrack what I'd changed in the schematic until I could get an error-free sync. Recently I found there are a couple things that I can do to quickly and easily fix these problems in 99% of cases.
First, if I get a message about unmatched nets, it's usually because I reassigned a wire to a new net. Altium doesn't like it when you just change net names between syncs. (Although it's usually fine if you remove a net name and then re-add a new name to the wire.) Anyway, whenever I get errors about unmatched nets in Altium now, I just save the whole project, open up the PCB file, and reset all of the PCB nets (Design » Netlist » Clear all Nets). After doing that, the next sync usually just works. If not, I can revert back to my save and do a bit more digging.
The second common error I get when syncing is a failure to match unique identifiers. This usually happens when I copy and paste parts in the schematic and then do a sync. To fix this, I open up a schematic in my project and reset all of the unique component IDs (Tools » Convert » Reset Component Unique IDs).
The the box that pops up, I usually go for the nuclear option: "Reset All Component Unique IDs" and "All schematic documents in the current project". (Don't ask me why Altium switches between title-case and sentence-case.) I haven't run into any negative effects from reseting the unique ID for every component in my projects.
Photo by Simon Claessen