Install latest windows updates.
Install Microsoft NET 4.5 directly from Microsoft web site:
Reboot PC and do a clean install of SAGE 50 2016 full version

Resolution for '32 System issue: 'Error ” Microsoft NET Framework Method not found:Int 32 System.Runtime.InteropServices.Marshal.SizeOf(!!0)' available: Yes.

The 32 System issue or error code is a known related to Sage Accounting products. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the 32 System issue yourself by looking for a resolution described in the article. If it is a complex 32 System issue or you are unable to solve the issue, you may contact Sage Repair by clicking here or by using other 32 System support options.

For more information about resolving issues related to 32 System in Sage Accounting or to get support for the issue 'Error ” Microsoft NET Framework Method not found:Int 32 System.Runtime.InteropServices.Marshal.SizeOf(!!0)', click the link below: