Google has confirmed a bug with Google ads impacting conversion data. The issue is specific with Google Ads conversions that use non-First/Last Click attribution models, such as Data Driven Attribution (DDA).
Google said the data may be delayed up to 24 hours and is working on fixing the pipeline delay.
Google posted this at about 3:22pm ET on Tuesday, December 21st over here saying "we're aware of a problem with Google Ads affecting a significant subset of users. We will provide an update by Dec 22, 2021, 1:00 AM UTC detailing when we expect to resolve the problem. Please note that this resolution time is an estimate and may change. The affected users are able to access Google Ads, but may not have access to the most recent data."
Google's Ads Liaison also responded to some complaints about the data being delayed:
Hi Simon, The team is aware and working on this. You can find the latest updates on this issue posted here: https://t.co/iMuQ6lIMxp
— AdsLiaison (@adsliaison) December 21, 2021
Google fixed the issue at 6:07pm ET the same day, Tuesday, December 21, 2021. Google wrote "the problem with Google Ads has been resolved. We apologize for the inconvenience and thank you for your patience and continued support. The affected users are able to access Google Ads, but may not have access to the most recent data." Google added "conversions delayed by this incident, those making use of non-First/Last Click attribution models, are now present in Google Ads."
Hi Shaun, It was a reporting delay and bidding was not impacted.
— AdsLiaison (@adsliaison) December 22, 2021
Forum discussion at Twitter.