Stop the Portainer container:
docker stop "id-portainer-container"

Run the helper (you’ll need to mount the Portainer data volume):
docker run --rm -v portainer_data:/data portainer/helper-reset-password

If successful, the output should look like this:
latest: Pulling from portainer/helper-reset-password
79916c70cb9e: Pull complete
93e26fa95550: Pull complete
Digest: sha256:735a809b1bfe14b5fae340d4b350bae97c2016371c47fb6e34d71a45e4512f79
Status: Downloaded newer image for portainer/helper-reset-password:latest
2022/03/11 18:45:07 Password succesfully updated for user: kayaks
2022/03/11 18:45:07 Use the following password to login: X<f5^83s0u)Heirg+2oC1`=q&nz

Start the Portainer container then try logging in with the new password:
docker start "id-portainer-container"