Please fill out the fields below so we can help you better. Note: you must provide your domain name to get help. Domain names for issued certificates are all made public in Certificate Transparency logs (e.g. crt.sh | example.com), so withholding your domain name here does not increase secrecy, but only makes it harder for us to provide help.
The operating system my web server runs on is (include version): Windows 2022
My hosting provider, if applicable, is:GoDaddy
I can login to a root shell on my machine (yes or no, or I don't know): No
I'm using a control panel to manage my site (no, or provide the name and version of the control panel): Plesk Obsidian 18
The version of my client is (e.g. output of certbot --version or certbot-auto --version if you're using Certbot): Don't know
I received an email saying my Let's Encrypt certificate is due to expire on 14th April 2024, but it's for a subdomain I don't own. I own lifewave.com and lifewaveevents.com, but this SSL is for lifewaveevents.lifewave.com. Please advise.
Usually you "own" the root domain name and can setup subdomains for it as you wish. So, lifewaveevents.lifewave.com is just a subdomain of your owned livewave.com domain.
Someone got a cert for that name on Jan15 2024 (see link here) and to do that must have demonstrated control over that name. Usually either an HTTP Challenge involving an A record pointing to a web server to handle that name. Or, using a DNS Challenge which places a TXT record in your DNS to prove control. It may not have been you explicitly but perhaps something did that on your behalf.
You said you are using plesk. This domain you do not recognize looks like a combination of lifewaveevents and lifewave.com. Could you have setup something in Plesk in error which setup such a subdomain and then gotten a cert for you? This looks like a common kind of typo setting up domain name.
Because if it wasn't your mistake then someone got control of your DNS and then issued a single cert wrongly. I do not think this is likely.
There was only that one cert issued on Jan15 for that name. None since. You won't receive any other emails about it.