Error "You are not allowed to make changes to budgets" when creating AccountBudgetProposal with Google Ads API

I'm trying to create an AccountBudgetProposal using the Google Ads API (v14), but I keep encountering the following error: Request with ID "" failed with status "INVALID_ARGUMENT" and includes the following errors: Error with message "You are not allowed to make changes to budgets." On

Issue with Creating camp Display Upload Ad in Google Ads API v14 - python

I'm trying to create an display upload ad in Google Ads API v14, but I'm encountering issues. Specifically, I'm getting an "INVALID_ARGUMENT" error with the message "Mutates are not allowed for the requested resource." def create_display_upload_ad_group_ad( client, customer_id, ad_group_id,