I apologise for the inconvenience

Lotus was running on a one year validity server certificate which expired as of 19th August as correctly reported here

The certificates are now renewed. You can update your lotus install but will need to delete the mainnet folder and run 'lotus init' to reinitialise the auxialliary certificates derived from the lotus_ca.

Don't forget to back up config.yaml or the db folder. Although the database is small and can be resynced easily.

What a way to celebrate a 1 year anniversary !