I might be missing something, but artifacts for the new 0.13.5 version don't seem to be on maven central. This is what sbt is trying to resolve, and it indeed doesn't seem to exist:
https://repo1.maven.org/maven2/io/github/timwspence/cats-stm_2.13/0.13.5/cats-stm_2.13-0.13.5.pom