project references package System.Text.Encoding.CodePages version 4.3.0 which is alright.
the published nuget is probably built against net46 resulting in reference to assembly System.Text.Encoding.CodePages, Version=4.0.2.0 (package 4.3.0 contains assembly for net46 with version 4.0.2.0) .. this causes anyone using this package on netstandard properly referencing System.Text.Encoding.CodePages 4.3.0 but on platforms != net46 the runtime crashes with FileNotFoundException