When the PATH environment variable gets overloaded with too many values it reaches a point where you cannot add values any more. Trying the following should solve your problem.
Solution 1:
Create a new system environment variable, say 'NEWPATH'
Assign the bin directory location to 'NEWPATH'
Now append '; %NEWPATH%' to the PATH environment variable
If this still doesn't work then try to copy some part of the PATH environment variable already existing values to the 'NEWPATH' and then append the 'NEWPATH'.
Solution 2:
Check the value of the PATH environment variable if you can group and shorten the paths. For example,
C:\Program Files\Microsoft SQL Server\102\Tools\Binn;C:\Program Files\Microsoft SQL Server\102\DTS\Bin;
can be combined to
C:\Program Files\Microsoft SQL Server;
In this way, you can build more space into your fixed length PATH variable and finally adjust your bin directory location into PATH.
