Why the new web part (farm solution only) can't be inherited by web applications ?

Question

Hi everyone,

I has a share point farm which has two web applications: http://xxxx:2880 and http://xxxx:2890(they are in the same host).

Those web applications will install the same farm solution *****.wsp。

And there has network load balancing feature (on another host machine we has the web applications with same ports).

When we visit share point we use https://teip.***.com.cn/headquarter instead of http://xxxx:2880.

And for some reason, we need add a new web part (farm solution only). We finished it by clone a worked web part in the solution.

When I deploy it I use following commands as administrator character:

Uninstall-SPSolution -Identity ****.wsp -Confirm:$false -Verbose -AllWebApplication -Confirm:$false
Remove-SPSolution -Identity ****.wsp -Confirm:$false
Remove-SPSolutionDeploymentLock -Identity APPSSP2013MASTERKONG.wsp -Confirm:$false
Add-SPSolution -LiteralPath *:\****\****.wsp -Confirm:$false
Install-SPSolution -Identity ****.wsp -WebApplication http://****:2880 -GACDeployment -FullTrustBinDeployment -Confirm:$false
Install-SPSolution -Identity ****.wsp -WebApplication http://****:2890 -GACDeployment -FullTrustBinDeployment -Confirm:$false

After that, I can find the web part in web part gallery from the path "Site Settings -> Web Desinger Galleries -> Web Part"

Whe I navigated to the web application. I can't find it in web gallery. 

I wondering whether network load balancing caused it. But I'm not sure. Who can help me out? 

Yang Xu