We installed the extension successfully on M2.2.11 CE but on catalog price reindex we got an error 

PHP Fatal error:  Uncaught Error: Call to a member function registerTags() on null in /vendor/magento/module-catalog/Model/Indexer/Product/Price.php:80 


The root of the issue is that version 2.2.1 for M2.2.6-2.3.0 is not compatible with M2.2.11.

To solve it, we have fixed file 


Please apply the fix on the site.

If you need any further assistance, please feel free to contact us.

We're more than happy to support you.