You inserted an absolute (full) URL into the URL field.
You shouldn’t be seeing “https:” anywhere in the middle of URLs.
Therefore, you have added https:/eu2.make.com/api/ incorrectly somewhere.
If you read the description below it, it says:
Enter a path relative to https://__________ … For example: __________
So you simply need to OMIT the first part of the URL that will be added for you.
Hope this helps! If you are still having trouble, please provide more details.
— @samliew