Starting January 31, 2017, AdWords no longer supports the creation or editing of standard text ads (STA). New text ads generated after that date should use the expanded text ad (ETA) format.
The exact steps you need to do for the migration are:
1. Log in to BBM.
2. Go to step 4, Ads.
3. Here you can already find the new ETA templates. They should already be filled out with the content you have on your current STAs.
4. The second Headline needs to be filled out.
5. Check that every field of the different templates are fine (look at the outcome on the right side).
6. Once everything is fine, click "Proceed to the summary" and finish the process in the last step.
It might take a few hours until the new ETAs are available on AdWords.
More info about Expanded Text Ads can be found at Google support.