Likely save game incompatible.
Planet portrait changes and additions (causing the incompatibility with older version games);
New biosphere level;
New atmosphere modifiers added to dynamic habitability (why you should start a new game anyway);

refer here for more information:
https://www.patreon.com/posts/atw-main-mod-105762833?utm_medium=clipboard_copy&utm_source=copyLink&utm_campaign=postshare_creator&utm_content=join_link

Bug fixing related to planets getting nuked by event. If one if your planets or one you know about is nuked by an event and the modifiers are not changed, you need to save and reload, it should fix the issue, if not, report it;

Red Dwarf systems were made more common, should also help with larger galaxies as these usually have less planets;

Gaia worlds now get their alternate variant influenced by the deposits spawned, for instances if it has a Searing Desert it will increase the odds of being converted to a Thermogaean, but this may not always happen as the presence of Fertile Fields for instances will also increase the odds of getting a Chloerosgaean. The biggest modifiers will be Crystal Reef (chloeros), Dust Desert (thermo) and Fuming Bog (cryo).

This also happens when you terraform to gaia, and if your species has the ocean paradise origin, you will get an Okeanosgaean.

Included most of Planetary Diversity's vanilla replacements;
other minor things

Updated to 3.12 / new DLC.

Bug fixing.
If you find a planet with missing modifiers or a colony with wrong portrait, save and load. If the issue persists, report.

Marginal and Sub-marginal worlds (except regular Tomb worlds) no longer spawn during galaxy generation as habitable.
They spawn as uninhabitable, identifiable as Telluric, Toxic, Cratered or Magma, and you will be able to build a mega project on them which does the necessary conversion to enable colonization.
An alternate project keeps them as uninhabitable but spawns a mineral deposit (Machine empires only have this option).
For more info:
https://www.patreon.com/posts/101305418?pr=true

Tomb World Restoration and Geographical Survey decision bug fixes.

Added a script that checks every galaxy regular planet for missing or wrong planet class modifiers, only runs on loading a saved game. Some vanilla events or even other mods may change a planet class during the game, but the old modifiers will remain, if this happens, just save and load, should correct all modifiers.