So i built my first weapon stand in Sanctuary Hills settlement. I assign a settler to the weapon stand but they never post up in and therefor i cant barter at the shop. How can i fix this? Thanks in advance.

It takes time for the settler to serve as a vendor after assignment. Each time I assigned one, I left. When I returned, the shop was open and being serviced in the day. If your settler isn't working the shop after fast traveling out and back in to your settlement. Try assigning a different worker. Otherwise...

Is there space behind the counter for the settler?

Is there a clear path for them to get behind the shop?

Are you sure you assigned a settler and not a provisioner?

Use the bell to call your settlers. In workshop mode hover over your shop keeper with the shop in the background. If the shop and your worker have a green highlight, then that worker is assigned to that shop. This works for all workers and their assigned job locations.

yup tried all of the above still no luck

Having the same issue with Armor/Weapon shop, simply wont go there. Bar, Clothing, General goods work perfectly.

Weapon Stand tier 1 was bugged for me and a settler would never attend it, no matter which settler I assigned or where I put it. Tier 3 worked fine though. All my tier 3 stands work right. I advise trying another tier.

Do keep in mind the shops keep certain daytime hours and they settler may not attend it the same day you assign it. Pathing can be an issue as well and sometimes settlers just seem to randomly take a day off.

I have had mixed results. Sometimes a settler never goes to the shop but just stands somewhere. I can go find them because I have gotten used to where they stand, and interact with them to barter no problem. Once I had a weapons merchant in Sanctuary that liked to do business in my garden. Then I scrapped the lvl1 stand for a lvl2 stand and reassigned the same settler and this time went to the stand every day instead of my garden. Don't know why...

I wonder if storing the non-working stand in the workshop and then replacing it somewhere new would fix the issue?

As others have said - all tier 2 and 3 shops assign just fine.

Some tier 1 shops, in particular the many times reported tier 1 weapon shop is either bugged or affects enough players it is a safe assumption to consider it off limits - save caps and start with tier 2 weapon shop to avoid assignment issue.

Mine seem to be picky as to when they actually get up there and begin vendoring. It's a bit annoying, but mine get there. Eventually.