These errors occur when the first argument to plots:-pointplot or plots:-pointplot3d is not a set of points of numeric values specified in the proper format.  For the correct syntax, see the plots:-pointplot and plots:-pointplot3d help pages.

Example 1

The variable $x$ is undefined:

Solution:

Defining the variable fixes this error.

Example 2

Lowercase $\mathrm{pi}$ is used instead of uppercase $\mathrm{Pi}\.$

Solution:

Using uppercase $\mathrm{Pi}$corrects the error.

You can also use the $\pi$ symbol from the Common Symbols palette.

Note: In Maple 2017 and earlier versions, error message that occurs in these examples is slightly different: