In the latest versions of Excel 365, Microsoft has made a change that causes a conflict between Real Statistics and Solver. Since Real Statistics requires the activation of Solver, this is a problem.
This issue and its solution is described in detail at:
Conflict between Real Statistics and Solver
As described on this webpage, I suggest that you install the latest version of the Real Statistics software, Rel 6.4.1, which will address this problem. Make sure that you install this version as described on the webpage.
This new release will also address a bug in the KSSTAT and KSTEST functions when data is in the form of a frequency table and the midpoint approach is desired.
Note too that the Mac version of Rel 6.4 is now available. As far as I am aware, the incompatibility problems with Solver does not affect the Mac version of the Real Statistics software. Also the bug in the KSSTAT and KSTEST functions was already resolved in Rel 6.4 for the Mac.
Charles