mcrypt is depreciated
Need to have a alternate / up-to-date solution.
We’re working on adding an alternative in our next update. :-)
With Wordpress now recommends PHP 7.0 as the minimum requirement and now PHP 7.1 available, mcrypt is not available for either branch. Mcrypt can be found for PHP 5.6, but you have to really hunt it down as only a few distributions have it and it is really out of date.