It is a common problem with Hugo. Here's what you can try:

Open your repository, click settings, and select pages. In the Build and Deployment, select GitHub actions. You will see some suggestions like Jekyll. Type search other existing workflows and search for Hugo. After selecting the default hugo.yml, this file would be added to .github/workflow directory. Your website will be re-deployed in a few minutes.

Also, check that:

• in settings/actions: Workflow permissions are set to Read and write permissions.
• you have a gh-pages branch in your repo