You need to make sure that your grid view isn’t filtered or grouped by any calculated fields.

— ScottWorld, Expert Airtable Consultant

It's happening on all tables of that database

You can also press shift-enter to create a new row. If that doesn’t work and your grid isn’t filtered/grouped, then be sure to email support@airtable.com about it. 

Hmm, so you're saying that when you open the record details and hit enter in a long text field, it's not going to the next line? 

Hi Lou,
Just want to chime in here to ask whether you have installed any browser extensions.
Further try using Airtable on a different browser and see if the problem persists?

I've seen this happen (since a day or two) with single line text fields in forms on PC (tested on Edge & Chrome). On a Mac it works as before (enter in a single line text field on a form actually grows the field). 

If that's correct or not is open to debate, but the behavior has changed on PC now. The workaround is to change the field to a long text field. No fun if you have a lot of forms of course.

Same thing is happening to me! It's very frustrating. 

This did not work for me. Any other suggestions?