Usually accessible in less than a week from submission. There has been speculation that ECAS access is made available after documents are uploaded to GCMS.
To access ECAS on the below link, choose Identification Type as Application number/Case number and enter your EE id "Exxxxxxxxx". Input other details carefully especially the DOB field because on some devices and/or browsers, it has a different format. On Chrome, the input field shows up as DD-MM-YYYY even though the field name says YYYY-MM-DD.
All the best!