It is using the legacy syntax which was deprecated 6 months ago and fully removed in this months release. It looks like you changed 2 keys but didn't actually update the structure. By the looks of it, the provided config is likely configured directly under sensor (as was the case in your post 6 months ago) or in a file that is using sensor as its top-level key, meaning they are part of the sensor integration. Template entities need to be configured with template as their integration.
the platform key is no longer used for Template entities.
the sensors key is no longer used for Template entities.
the value_template key is no longer used for Template entities, it has been replace by state.
The availability_template key is no longer used for Template entities, it has been replace by availability.
The friendly_name key is no longer used for Template entities, it has been replace by name.
ID slugs are no longer used for Template entities, there are various configuration variables available to provide entity names and IDs.
The easiest way to fix this will be to change state and availability in power_current back to their original keys, then run the tool Petro has provided in the deprecation threads.