I have the same problem but the difference is i have the google form embed in iframe tags for over a year. then suddenly this morning when i check my website, the embedded google form in pages stop working and only show a blank page.
The solutions:
1. First check whether the iframe tags are working correctly: https://www.w3schools.com/html/tryit.asp?filename=tryhtml_basic
sim
Simply replace your iframe tags in the body and submit the codes. If it is working then all is good.
2. Search from your plugins page: WordPress Google Form or download from here: https://www.ads-software.com/extend/plugins/wpgform/
simply follow the instructions and all working perfectly in wordpress.
Good luck!