Native dll

is the dll you are importing 32 or 64 bit? are you running Community as 32 or 64 bit?

The native dll was 64 bit. Our local job service is also running on 64 bit .

But the target community is on Telligent saas.

Are you trying to run a job service locally that Telligent Saas communicates with? or is this just for dev?

Either way, this error seems to primarily relate to a mismatch in bitness between a dll and the environment. Ensure all components are loaded in environments with matching bitness. Also ensure any customizations are loaded to the web server and the job server for consistency.

I have just found that the jobserver is running on x86 , how can I force it to run under X64 

Here's a previous thread discussing ways to do this:  (Missing Forum Reply)  

To work around this, you need to either run the Job Server on a 32-bit OS, or use the CorFlags utility in the .Net SDK to remove the 32 bit preference. (coreflags.exe Telligent.Jobs.Server.exe /32BITPREF-). See https://msdn.microsoft.com/en-us/library/ms164699%28v=vs.110%29.aspx?f=255&MSPPError=-2147217396  for more details.