The endpoint for the Prometheus / Grafana metrics has changed from /metrics to /prometheus/metrics from version 1.1.0 onwards.
You will need to modify your /etc/grafana-agent.yaml file to include the metrics_path: /prometheus/metrics under the job_name row:
Before:
prometheus:
configs:
- name: integrations
scrape_configs:
- job_name: my_job_name
static_configs:
...
After:
prometheus:
configs:
- name: integrations
scrape_configs:
- job_name: my_job_name
metrics_path: /prometheus/metrics
static_configs:
...