The Odin Serializer has two sets of assemblies; One set for AOT platforms and one for those platforms where JIT is supported. JIT is usually the most performant, but it is not supported on all platforms. Finding out whether your setup supports it goes beyond what Unity's import settings have to offers.
If you built with JIT, with built settings that do not support it, then you will encounter errors when Odin tries to deserialize any of your data.
You can change the import settings from the import settings preferences, found at Tools > Odin Inspector > Preferences > Import Settings.
Odin has a predefined set of known setups where JIT is supported. If your setup doesn't match any of those then it'll choose to use the AOT assemblies.
Enabling the "Automate Before Build" will enable a preprocess build step, that will configure the import settings automatically based on your current build settings. This feature requires Unity version 5.6 or newer.
If you've stumbled on a setup where we're using AOT when we could be using JIT or the other way around, then you can always disable preprocess build set and manually configure your assemblies.
We would also very much appreciate it if you reported this to us so that we can address this in a future version of Odin.