The addon could not be enabled because it generated a fatal error:
I just enabled the Articles app on a fresh install of Vanilla 2.1.8p2 successfully and didn't get this error. Does enabling debug mode in the Vanilla config show more details about the fatal error?
Add Pages to Vanilla with the Basic Pages app
Found a permissions problem on conf due to file permissions being messed up when moving files around when upgrading vanilla on that install.
Works now. Thanks.