Pushing to a protected branch using OAuth

[David Connack]

Hello.
Im trying to push to a branch that is protected using OAuth as described here.
Ive followed the documentation, but im still getting the following:

! [remote rejected] main -> main (pre-receive hook declined)

error: failed to push some refs

My script looks something like this (simplified and scrubbed)

#!/bin/bash

export access_token=$(curl -s -X POST -u "${CLIENT_ID}:${CLIENT_SECRET}" https://bitbucket.org/site/oauth2/access_token -d grant_type=client_credentials -d scopes="repository"| jq --raw-output '.access_token')
git config user.name <authorised user>
git config user.email <authorised email>
git remote set-url origin "https://x-token-auth:${access_token}@bitbucket.org/${BITBUCKET_REPO_OWNER}/${BITBUCKET_REPO_SLUG}"
echo "Now using git authenticated."

sed -i "/^\([[:space:]]*tag: \).*/s//\1$TAG/" values/envs/"$ENVIRONMENT"/"$SERVICE".yaml
git commit -a -m "[skip ci] updated image tag $ENVIRONMENT $SERVICE tag to $TAG"

git push

Everything works as expected without the branch protection rule.
Any ideas?
Thank you