Kibana Uptime- Internal Server Error

ELK-Stack Version: 7.8
Installed and configured Heartbeat agent on a linux server and the ping/logs are being ingested into elasticsearch. I do see the logs being populated under "heartbeat-7*" index

But when I visit uptime dashboard on kibana I see the below error "Internal Server Error" also the left most total "Monitors" count is not populating as expected.

I would request any help/suggestion on this issue

While debugging I notice the below error:

Kibana-Reference - I've enabled-configured the elasticsearch username & password

Can you share your kibana logs? There should be an error there. We'll need that to debug further.

Until yesterday, I was ingesting heartbeat events to kibana via logstash and I was facing the error.
Today, I tried ingesting heartbeat directly to elasticsearch by adding output.elasticsearch and it's worked well. Now I see the uptime and TLS cert info

Currently we do have many hosts to monitor for uptime & certs. I referenced this link Heartbeat
and tried passing my hosts in each individual .yml files (/path/to/my/monitors.d/*.yml)

  path: ${path.config}/monitors.d/*.yml
  reload.enabled: false
  reload.period: 5s

and inside the monitors.d, I created a new file with .yml with below config but I don't see the host event being reported on uptime

- type: http
  id: <unique id>
  name: <monitor-name>
  hosts: ["https://<hostname>:443"]
  schedule: '@every 60s'

When I start the heartbeat, I don't see the logs in heartbeat index and in uptime monitors. But If i specify the hosts in heartbeat.yml directly I see the logs and metrics

@Andrew_Cholakian1 Please review & suggest