The problem, which concerned the configuration of the subscription key, came up on Tuesday night. The applications had a problem downloading the diagnostic keys from the servers. Some of them displayed a notification on the loading screen that users were unable to dismiss by sliding their finger. Rebooting the device can eliminate it, but you should not wipe storage in the app. This will not solve the problem and may cause data loss and possible exposure matches.
Applications continued to collect keys (which are used to track contacts) and track potential exposures while the problem remained active. Google engineers will work with application developers to fix any remaining issues as quickly as possible.
Google collaborated with Apple on a contact tracking system, which was launched to public health agencies last May. However, it does not appear that the problem affected iOS exposure notification apps.
Update 13/01, 2:45 ET: Updated to note that Google has issued a correction.