I click on "Edit HTML", and the editing display opens - but the HTML window remains blank.
Generally, you may wait a few seconds, and the HTML window will fill with the content. With enough patience, you'll see the content arrive - eventually.
Unfortunately, waiting won't always provide a solution.
Sometimes, you see the Template Editor display open, with a blank HTML window - and you wait patiently, with no result.
With the Template Editor display (common to every blog, and requiring no security) - and the Template HTML (unique to every blog, and requiring security) - coming from different servers - there's always the possibility that a dropped connection, from the Template HTML server, may cause the browser to time out.
In many cases, this will be a transient error. All that you need to do is to refresh the display.
- Try a browser refresh. F5, or maybe Shift - F5, forces a refresh, in most browsers.
- Restart the Template Editor. Click on Template, then "Edit HTML", again.
- In extreme cases, clear cache, cookies, and authenticated sessions (since this is secure content, you'll need a new authenticated session) - then restart the browser, and start over.
If the lost connection is not transient, your Internet service may be part of the problem. If a simple refresh does not solve the problem for you, you may want to look at the MTU setting, on your computer.
An overly ambitious Maximum MTU setting could cause a chronic or persistent dropped connection, with the Template HTML server. Lowering the Max MTU setting could resolve this symptom.