Hello. I have used plugin Bubble Page to PDF converter Plugin | Bubble Thank you for great job. But now I have error. Could u help resolve it?
Hello, @volgobur. Thanks for reaching out.
Please forgive me for my late reply.
From the screenshot you have it’s quite difficult to tell what can cause it, so let me please make a few suggestions and request from you some details. 
First of all, the error you receive might appear if you are using in the plugin action field Convert target = Single element and indicated (or not indicated at all) the wrong ID in the ID field. Correct means here the proper ID of the element you want to convert - it should be the same in the plugin action field (ID).
Second of all, to be sure you have the correct setup, please share with me some information about what you are trying to convert (page, its parameters, and conditions when you want to convert it), plugin action screenshot (the full action screenshot to let me see all fields). You can also record a Loom video showing those parameters and reproducing your case.
Thank you.