Reviving data from an unresponsive Lightsail instance

I'm relatively new to sysAdmin concepts, and I've been running an Amazon Lightsail instance on Ubuntu 20.04 LTS with 1 GB RAM and 2 vCPUs. I had set up InfluxDB, Telegraf, and Grafana to collect and store measurements over the past 3 months. Recently, I had to reboot the instance for an update, and after the reboot, I'm unable to establish an SSH connection. I suspect this issue might be related to the substantial data stored in InfluxDB, which starts at system startup.

I attempted to recover the data by creating a snapshot of the Amazon Lightsail instance and exporting it to a more powerful EC2 instance, but the problem persists.

I also tried exporting the snapshot to an EC2 instance, detaching the volume, creating a rescue instance, and attaching the volume to access system logs or potentially extract data, but I couldn't successfully mount the volume to a live EC2 instance.

Could anyone provide guidance on resolving this issue?

P.S.: I originally connected to the instance using a keypair, and I haven't created another user with a password to access the instance via the EC2 serial console.