Your best bet is to either use the old form view, or to use Fillout’s advanced forms for Airtable, which lets you update records from a form with no prefilling at all.

There is some sort of a bug in Airtable that prevents the prefilling of linked records in interface forms.

If I remember correctly, if you have certain rules set on your linked record field (in the right margin of the interface form editing screen), then you are no longer able to prefill the form through the URL.

So try removing all the rules in the right margin, and see if that fixes the problem.

If you figure it out, be sure to email support@airtable.com to report it as a bug.

Otherwise, you can either go back to the old forms, or you can update records through a form — without needing to specify any prefill values at all — by using Fillout's advanced forms for Airtable. 

Fillout is 100% free, and it offers hundreds of features that Airtable’s native forms don’t offer, including the ability to update Airtable records using a form, create custom PDF files from a form submission, accept payments on forms, pre-fetch dynamic data from an Airtable record, display Airtable lookup fields on forms, create new linked records on a form, add a login page to your form, perform math or other live calculations on your forms, collect signatures on a form, create multi-page forms with conditional paths, connect a single form to dozens of external apps simultaneously, add CAPTCHAs to your form, and much more.

I show how to use a few of the advanced features of Fillout on these 2 Airtable podcast episodes:

• Using Fillout to create an eSignature approval process with PDF file creation.
• Using Fillout to create an order entry form with line items.

Hope this helps! If you’d like to hire an expert Airtable consultant to help you with anything Airtable-related, please feel free to contact me through my website: Airtable consultant — ScottWorld

Hmm, I just tested this and it works fine.  Here's an example:
https://airtable.com/appcXaMJes8r6tvCb/pagrmrd11MppM0OMr/form?prefill_Table+1=reclzAX1bvUWRSwJE
Link to base

Could you provide some examples of the full URL you've created that's not working?

Hi Adam @TheTimeSavingCo  - following up on this since there seem to be many people with this issue.  I was able to get mine to work and then it stopped working.  I see yours does work.  I looked at your base as well.

Can you also share your formula for comparison?  Thanks!

Ah, it's just `record_id()`

I was able to get it to work but the issue is that you have to click the reset button to get the values to populate. This is not acceptable to do for my employees workflows. Is Airtable working on this?

Hate to +1 but yeah I'm running into this issue now too. 

Hi everyone!

To help you get more out of Airtable, at miniExtensions, we've built a versatile third-party form. Our form can prefill hidden fields without including them in the form structure or the URL itself. Additionally, we provide the option to automatically submit the form after pre-filling, streamlining the process further.

To take this even further, you can create unique URLs for existing records, which can act as a foundation for generating new forms. These pre-filled forms allow you to edit the fields while maintaining reusable sets of pre-filled data that can be used as templates.

As you can see above, the URL only requires the record ID to prefill the whole form.