My hatch developed a few issues while sitting in quarantine. First, it wouldn't stay open and I replaced the struts today, no problem. But now it won't "shut" (I should have fixed this part first before the struts but alas) so my dash is always alerting that the back door isn't shut entirely. I tried looking up a few videos for a DIY fix but not finding exactly what I need. Any ideas before I call the shop?

 

Was it shutting OK before you changed the struts? If it was, perhaps the new struts are too long.
If it was not OK before, there's a little bit of adjustment on the trunk lock or catch bolts.
Trap a dollar bill between the hatch & the rubber seal & you can judge how tight it is when you pull it out.