The Heavy Armor Master Feat gives a +1 to Strength. This is accurately reflected on a character's sheet, but not on the Abilities tab when creating/editing a character. It should appear as a Misc Bonus. If you go to the Character Sheet, and then back to Character Builder > Abilities tab, the bonus is then accurately reflected.

I've tested this by creating a new character, Human (Variant), Fighter (level 1), going back to race and adding Heavy Armor Master as the feat, advancing to Abilities and seeing the Strength bonus is not reflected.

+1

I reported this bug once, but got no response. It seems like the ability score tab in the editor only updates when you choose an ASI or a Feat where you can select the AS to increase. Basically the editor only checks for updates when you change the selection in a dropdown menu and not when the ability score increases only in text, like with the HAM Feat.

It does no harm to your character stats in the end, but can be irritating when trying out a new build.

Refresh on Abilites page.

Quote from Cyb3rM1nd >>

Refresh on Abilites page.

Yep, that, like advancing to the character sheet, will get the bonus to be reflected accurately. But note this is not required for other feats that grant an ability score increase, such as Athlete or Observant. The bonus for these is reflected without having to perform any additional steps outside the normal character creation progression.