Nintendo team released a new firmware for Nintendo Switch -6.1.0. You can check the changlog in this post.
Latest version: 6.1.0 (Distributed 10/29/2018)
Improvements Included in Version 6.1.0 (Distributed 10/29/2018)
General system stability improvements to enhance the user’s experience, including:
Resolved an issue where certain games don’t recognize a Nintendo Switch Online membership for a short time after purchase
SX Pro, SX OS and AceNS all work on Nintendo Switch firmware 6.1.0.