This message is generated when Root is used with a polynomial for which the polynomial degree does not have the indicated form.
The limit $MaxRootDegree on the degree of a polynomial in Root is included to prevent calculations that would otherwise be prohibitively time-consuming.
Off[message] switches off the message; On[message] switches it on. For example: Off[Root::mdeg].
Examples
Basic Examples(1)
With the default value of $MaxRootDegree, this input will generate an error, and the root will not be computed: