Adaptive plans bypassed - but why ?

I have a SQL query - in 12.1 it was using Adaptive Plan. In 12.2 it isn't anymore. I don't see this a big problem, but would like to be able to explain why.

Unfortunately I can not share the full 10053 trace, but I will be able to copy&paste all relevant parts - just tell me what you are looking for.

some probably interesting parameters:
AP - adaptive plans

optimizer_adaptive_reporting_only   = false
optimizer_adaptive_plans            = true
optimizer_adaptive_statistics       = false
optimizer_features_enable           = 12.2.0.1

I'm curious regarding these lines:

AP: Checking validity for query block SEL$3, sqlid=0zc1a01zycagh AP: Adaptive plans bypassed for query block SEL$3 due to materialized query block
AP: Adaptive joins bypassed for query block SEL$3 due to adaptive plans disabled

? why is a MV block adaptive plans?

? where can I find why adaptive plans are disabled?

Again, this is more for me to understand, right now there is no issue ;-)