You need to build strong named assembly. But your references has references to not signed dll too. Then for fix them you need to fix them references too.
Add as Pre-build events to first project of build order. Solution (right click) -> Project Build Order:
$(SolutionDir)tools\SignDllTool.exe /dir:$ (SolutionDir)packages /in:FluentValidation[.\d]+\lib\Net45\FluentValidation.dll;MongoDB.Bson;RestSharp[.\d]+\lib\net4[\d]*\;DotNetZip /key:$(SolutionDir)sign.snk
Where SignDllTool app for resign dlls with your snk. Solution based on Signing an Unsigned Assembly And argument /in:Regex - regular expression separated by ; for resolve path to dlls in argument /dir:
snk must be with private key without protection (password). Please see https://github.com/aarnott/pfx2Snk
makecert.exe -pe -n "CN=SignDllTool.Tests" -eku 1.3.6.1.5.5.7.3.3 -a sha1 -r -sv sign.pvk sign.cer
pvk2pfx.exe -pvk sign.pvk -pi 123 -spc sign.cert -pfx sign.pfx
pfx2snk sign.pfx 123 sign.snk