Can't connect through sqldeveloper because locale not recognized even though my language/regional settings are English/US On a certain machine I consistently cannot connect to an oracle db due to the locale not being recognized:

Other people have noted the locale or language settings may not be compatible with the oracle db driver but my laptop is US/English and I can connect to this same db w/o a problem from similar laptops. Moreover, I tried uninstalling sqldeveloper and wiping out all sqldeveloper folders under /AppData/Roaming/ so that I could not reimport settings during the reinstall but to no avail. Oracle db is 18c but this happens with 12c as well.  Sqldevelopers can be any version (ie 3.x, 4.x, 18.x, 19.x...yes, I've tried them all :( )
Try adding the following to your sqldeveloper.conf:

AddVMOption -Duser.language=en
AddVMOption -Duser.region=US