You were creating a new form for your campaign and you ended up with this error?
Sorry, this feature isn't available right now: An error occurred while processing this request. Please try again later
This bud doesn't have a solution right now, we are working with Facebook to solve it as soon as possible.
In the meanwhile, you may need to create your form directly on Facebook: later on they will be easily available on AdEspresso as usual.
----- Update 2016/05/19 -----
The problem seems to have been recognised and our request has been set Under Investigation
----- Update 2016/05/28 -----
Due to the lack of updates, we reiterated the request looking for a more timed response.
----- Update 2016/06/06 -----
Thanks for Facebook support, our developers were able to successfully solve this issue.