Do you have Kaspersky or other antivirus software installed? Or perhaps a Chrome add on that may be blocking the editor from loading? Many are reporting that Kaspersky is blocking the Tinkercad editor from loading.
The responsible Kaspersky component for this is the Web Anti-Virus and Network
Settings that can be found under Protection and Additional tab. You may need to allow www.tinkercad.com in this tab.
Disable Kaspersky blocking loading of designs:
1. Open Kaspersky Internet Security console
2. Click on Gear Icon in bottom left corner
3. Click on "Additional" tab on left hand side
4. Click on "Network" link on right hand side
5. Scroll window down till you see "Manage Exclusions"
6. Add "www.tinkercad.com" to exclusion list