I chose the Piercer feat at 8th level for my Ranger and it is not adding the +1 to Dex. 

Did you select Dex from the dropdown?

Yes I did. My base is 17, +1 from elven accuracy (verified it is on Dexterity score, and +1 from Piercer, also verified it is on Dex), so it should show as 19, but it is showing as 18. I manually adjusted for now. 

If you would like to get that sorted out, post the link to your character sheet so someone can take a look.

https://www.dndbeyond.com/characters/1678001

The bonus from the feat won’t show in the builder until after you look at the sheet itself. If you look at your sheet you’ll see that everything is working perfectly:

Hang on. If your Base is 17, then shouldn't your DEX be 19 with the +2 from being an Elf, even before factoring in the feats? Something's odd here.

One thing is for certain, you need to clear out the Override Score field.

Quote from naruhoodie >>

Hang on. If your Base is 17, then shouldn't your DEX be 19 with the +2 from being an Elf, even before factoring in the feats? Something's odd here.

One thing is for certain, you need to clear out the Override Score field.

 
Correct. It should be 20 because of the cap, but the override is bringing it down.

Now the issue I am having is that for example, the Arrow of frost +1 should be showing +10 to hit (+1 arrow, +5 for dex, +4 for proficiency, bow is not magical). Instead it is showing +17 to hit unless I override. The other items I did override because it is doing the same issue. Thanks for the help so far.

Those are a lot of homebrew weapons, which may be incorrectly coded. But if they all are messed up by the same amount then there's probably an incorrect modifier in one of them, I'm guessing a Bonus to Ranged Attacks or Bow Attacks, which actually applies to all attacks of that type and not just the item that has the modifier. Did you or your DM create the homebrews?

Also noticed with your Ability Scores that every score except DEX has an Override Score value, which you should clear out. DEX has a 0 in Other Modifier, which is unnecessary and should also be removed just in case that's messing with anything else.

Yes, the DM created the homebrews. I will clear out those scores like you suggested. Thanks again.

One thing you can do to narrow down the homebrew that affects other weapon attack rolls is to unequip each in turn and see when the attack rolls change.