Not all variable types are compatible with all Enfocus products. For example, "Text with Variables" can only be used with Switch. If a variable is "unknown" to an Enfocus product, it cannot be used or edited, but it won't harm either.
In Switch, some variable types are linked to a particular Switch module. For example, the "text with variables" variable using database fields is only supported if you have an active license for the Switch Database module.
The problem can also be linked to a rule-based variable; if the variable is based on another variable that has been removed or is invalid, the rule-based variable becomes invalid as well and gets a red exclamation mark in front of it.
If you want to use "unknown" variables, you must change the variable type to a type supported by the product you're using.
If you don't want to use it, just leave it in there; it won't do any harm. You can use (or edit) it again when working with other Enfocus products.
If you want to use variables that require a license that you don't have, please contact Enfocus to buy a license.
In case of invalid rule-based variables, review the rule(s) and correct or re-define the dependent variable(s) as required.