I am using Qgis 2.18.16, when i tried to download sentinel 2 via SCP interface, I am getting following error:
To download Sentinel data using the SCP-Plugin you must register first here. Once registration is complete, it is also likely to take a couple days before you are able to use an API, like the one incorporated in the SCP-Plugin.
More information is available in this official tutorial by SCP, where he explains:
"WARNING : The guest/guest account is not available anymore. Free registration is required. See https://scihub.copernicus.eu/news/News00097."
it is working now. it takes 24 hours after registration to work and guest login credentials are removed. so if anyone wants to download satellite data via SCP plugin in Qgis, one has to register using following link "https://scihub.copernicus.eu/news/News00097."