Invoke-NAVApplicationDatabaseConversion error

I am trying to convert a database from BC15 to BC 18.

I have followed this guide to Task4: https://docs.microsoft.com/en-us/dynamics365/business-central/dev-itpro/upgrade/upgrade-unmodified-application-to-v18

I get the error: Invoke-NAVApplicationDatabaseConversion : A technical upgrade of database 'MyDB' on server '***\' cannot be run, because the database�s application version '131050' is greater than or equal to the platform version '131050'.



I have read somewhere that it is just af warning, and I can just go on with the next tasks. But when I reach import version 18 license it shows an error, that The Dynamics 365 Business Central Server Administration tool can only manage version 18.0. The ServerInstance 'MicrosoftDynamicsNavServer$***' is Version '15.0.37898.0'.

I also have made sure restartning powershell and importing version 18 NavAdminTool.ps1 + opening as administrator.

I am not sure it has any relations but platform and application are different in the BC15 I am trying to upgrade:



Any ideas ?

I even asked Microsoft that guided me through different steps. Just to find out they did not know anything. So I learned the hard way not to ask Microsoft.

Instead I tried to upgrade directly to BC19 instead. That worked.