Ancillary file download requires an EarthData account . You can put your EarthData credentials "Username" and "Password" in the config/acolite_config.txt or your settings file:
Alternatively you can export them to environment variables which should be accessed by ACOLITE.
Edit 2021-08-11: Your EarthData account needs to have approval for the OB.DAAC Data Access and LP DAAC Data Pool to access respectively the ancillary data and SRTM DEM data. Login to your EarthData account to check Authorised Apps, and click Approve More Applications if necessary: https://urs.earthdata.nasa.gov/profile
I have added my EARTHDATA user credentials in the configuration file. However, while processing Sentinel-2a data for my region (Andaman) on 2020-01-31 the software is not downloading the ancillary data still. I'm unable to add the screenshots here to show. Kindly resolve.
Is it just the TOAST download that is failing, or all the ancillary data? I believe the TOAST files are no longer produced/distributed, so for recent files this will be changed in the code. If all files are failing, it may be an issue with your configuration.
It is possible that the failure is caused by a lack of the right Authorised Applications in your EarthData account - please check the edit of the first message in this thread!
As of 2023-10-16 the default ancillary dataset is GMAO MERRA2 data from OBPG oceandata server. These seem to be available after ~6 weeks, and for older imagery the new default setting can be used: