Cannot make the docs work get an gas error while making the meta tx docs work

Hi i am following this docs

this is the code snippet

i am facing issue here i want to enable gasless minting using metatx
here when i click on mint it i get a pop up and i sign the msg after that i get this error
i have manually set the gas limit in higher order of the estimate and my contract is compliant please help

I am unable to post the whole error as i am a new user

What is the error message, as far as I can understand it has got to do with non string value?