Cmd-K to go to Configuration, and make sure the Mythic Adventures source is checked for your hero's portfolio. When you acquire a new data package, it is not checked for pre-existing portfolios, only for new ones.
Yep, I checked that.
A bit more information that might be helpful to troubleshoot this: the list of errors is all of the format "Thing X - Bootstrap thing Y does not exist". The Y includes elements with codes My, MCh, and MAl. I can type in the entire error message if it would be helpful.
On the iPad, the only installed updates are Pathfinder Roleplaying Game v 10.5 and iPad Community Super Pack v 1.16. There are other items in the list of available updates (including ShadowChemosh Adjustments, d20pfsrd Community Player Pack, and some others) but I haven't installed those because I thought that the iPad Community Super Pack is supposed to cover everything that you need. I'm running iOS 8.1 and this is a brand new iPad.
On the Mac, I've checked all the various options (like Mythic Adventures) in the Configuration editor. I've also tried unchecking various elements to see if that would solve the problem but no luck. I'm running OSX 10.9.5 (i.e. latest version of last year's OSX) and I've confirmed that Hero Lab on the Mac has all available updates. In the update window of Hero Lab (Mac) I see multiple installed updates, including Hero Lab for the Mac V6.0a, d20pfsrd: CB Mythic Addon v1.2, d20pfsrd: Community Bestiary v2.25, d20pfsrd: Community Player Pack v2.24, ShadowChemosh Adjustments v2.10, d20pfsrd: SGG v1.7, d20pfsrd: Path of War v1.2, d20pfsrd: Gestalt v0.6, d20 Ultimate Psionics v2.5, d20 Eberron Setting v2.1, d20 Mythic Playtest v1.11, and various other updates for other games. As far as I know, I don't need any of these updates besides the Hero Lab for the Mac, the Community Player Pack, and maybe (?) also the ShadowChemosh Adjustments, but there's no option to uninstall them.
When I open my character's configuration window, I have ShadowChemosh's adjustments selected (this is the main thing I'm using the add-in for, though in the future as I start GM-ing I hope to use other elements too) and PFS Boons (as Vanities). I have none of the Modules selected (though they are available as checkable options). Besides that I have all the various elements for the packages that I've purchased checked, but I've tried unchecking them to see if that solves the problem and it didn't.