I recently upgraded to Scala 2.13.6 and I am seeing:
Error downloading org.scalameta:semanticdb-scalac_2.13.6:4.4.10
when I try to build.
I had a similar error when I upgraded to 2.13.5, but was able to add semanticdbVersion := "4.4.11" to build.sbt to get it to work.
This is not working this time.
You can check on the central Maven repository which versions of the project is available for which version of Scala:
https://mvnrepository.com/artifact/org.scalameta/semanticdb-scalac
The only version built for Scala 2.13.6 is 4.4.18 as of today.
This info is probably also available on their GitHub release note oages
I assume you are using the sbt-scalafix plugin in your build. This kind of error can happen if you update the scala version before you update the scalafix plugin to the latest version because the semanticdb version is usually set via this setting in your build.sbt (At least this is the official recommendation):
semanticdbVersion := scalafixSemanticdb.revision
In case of scala v2.13.6 I needed to bump the version of sbt-scalafix to v0.9.28 to fix the error you described.