Hi there! I understand you're using the CNBC app on your Mac running OS X 10.15.7 and you don't see a "Sign In" option, which is preventing you from accessing your watchlists or lists. Let's get to the bottom of this together.

First, just to clarify: Are you using the CNBC app downloaded on your Mac, or are you accessing CNBC through a web browser? Also, could you tell me if the app looks fully loaded or if some menu options are missing?

Assuming this is the CNBC app on macOS, here are some steps we can try:

1. Check for Updates: Sometimes, missing features like "Sign In" might be due to an outdated app version. Please check the Mac App Store for any updates to the CNBC app and install them if available.

2. Restart the App: Quit the CNBC app completely (use Command + Q) and relaunch it to see if the "Sign In" option appears.

3. Reinstall the App: If restarting doesn’t help, try deleting the CNBC app from your applications folder and reinstall it from the Mac App Store. Fresh installs often resolve UI glitches or missing feature issues.

4. Verify Network Connectivity: Check that your Mac is connected to the internet without restrictions like VPNs or firewalls blocking the app's access.

5. Check for App-Specific Sign In: Some users report that login features might only appear after starting to create a watchlist or similar content. Try looking for a “Watchlist” option — sometimes selecting that prompts a login screen.

6. Maintenance Windows: Occasionally CNBC performs maintenance that disables sign-in temporarily. It’s worth checking CNBC's official site or social media channels to see if there's ongoing maintenance affecting account access.

If you have already tried these or the "Sign In" is still missing, let me know, and we can explore more advanced troubleshooting or check account-side issues.

Does this make sense so far? Are you able to try these steps and update me on what you see?