Hi tlivings,
Thanks for contacting Apple Support Communities!
We understand that tags you've applied in Notes are missing sometimes.
What do you have set as your Default Account for Notes? You can go to Settings > Notes > Default Account to check.
Do your tags include any special characters? All tags must be single words as outlined here: Organize your notes with tags on iCloud.com - Apple Support
"Add tags to notes
You can type a tag anywhere in a note. Tags must be a single word, but you can use hyphens and underscores (for example, #meeting-minutes or #important_documents).
- In Notes on iCloud.com, select a note.
- Type the number sign (#), then type a word—for example, #meeting or #important—or choose from the list of suggested tags. (Suggested tags appear if you’ve already added tags in Notes.)
- Tags you add appear in the Tag Browser in the sidebar.
If you add a tag to a shared note, it appears as dimmed text to other participants who don’t have the tag in their Tag Browser."
If you're using iCloud as your default account for Notes, are you able to sign into iCloud via a web browser on a computer and see all tags in your Notes? You can sign into iCloud here: iCloud Sign In
We look forward to your reply.
Cheers!