I was having the same issue. It is because I used nvm to install the correct version of node.js and the startup service does not know the location nvm installed node 16. The below reddit thread explains it and the fix. Worked for me.
https://www.reddit.com/r/plexamp/comments/11qnfpb/comment/jc6l01o/
GitHub-flavored Markdown & a sane subset of HTML is supported.
Fill in your email address if you want to get notified when someone replies to your comment. Your email address is safely stored with strong 256-bit AES encryption. You can unsubscribe from notification emails any time by following a link on the bottom of a reply notification email.