FM Server 11 will only work with FileMaker versions 7 through 11.
You need at least FM Server 12 but FM Server 14 will work best.
There have been 2 big transformation with FMP: First with FM 7, second with FMP12.
There's no compatibility or interoperability between this generations
• until Filemaker 6
• FM 7 - FMP 11
• up from FMP 12
In most cases, there's a interoperability within this generations as long as no newer function shell perform on older versions.
For example: You can run FMP/FMServer 13 with FMGo 14, etc.