Season 3 is having some hiccups at its launch. It seems players can’t upgrade the seasonal companion, the Seneschal, and thus can’t progress the seasonal questline. Blizzard are offering some workarounds, however, as Community Manager Marcooose_ explains on the Diablo 4 reddit:
*Update: provided more accurate workarounds 12:39 PST
There is currently an issue in the Seasonal Questline where players cannot interact with the brazier to upgrade their construct and advance the quest.
The current workaround for this will be that players need to enter a new instance. This can be done by:
Closing the game entirely and re-logging
Changing World Tiers
Note that using a town portal will not work, because it opens the same instance.
The issue is being investigated by the team, and players should attempt the workaround until the issue is fully resolved, we’ll update here once we have timing for the fix.
You can read the entire official news post HERE