The Titantron Fix created by HanleysFramer is required for WWE 2k19 to be able to read custom Titantrons with IDs not originally available in the game (WWE 2k18 and earlier games have all trons activated by default, thus such a fix isn't required). It should also enable all Tron sizes for all IDs, even those that only have certain tron sizes enabled by default. It replaces the assetconv*.pac file relevant to the current game version with a patched version that enables titantrons for said IDs.
Note that the latest version of Custom Character Tools 2019 (CCT) also includes an easy-to-use installer for this Titantron Fix under the option Install Mods->Install "Titantron Fix" / Titantrons for all Slots.
In 2020, Squaredcirclefan released an updated version of the Titantron Fix that is newer than HanleysFramer's and also newer than the one included in Custom Character Tools which enables Titantrons for individual members of Tag Teams and a few more tron slots unlocked for both singles wrestlers and tag teams. Using this updated version is highly recommended.
Updated Titantron Fix for WWE 2k19 Information and Download by Squaredcirclefan (latest version, highly recommended!)
Titantron Fix for WWE 2k19 Information and Download (old, original version, also included in CCT)