Upgraded to 7.3 successfully
But the themes didn't work with me
When I want to change the theme appears a white page
Delete the boost theme and the following error appears
Default theme boost not available or broken!
How do I change the theme of the database
You must mean upgraded to 3.7.x of Moodle. ;)
Oops ... major theme changes to 3.7.x of Moodle. boost is a/the fallback theme used by moodle when other in-compatible themes are present. Thus deleting boost throws the error. (tip: never delete ... just hide core)
To get back to a point where you can see the newly upgraded moodle, add the following line to config.php of your site:
Classic was the other new theme that came with 3.7.
Check ownerships/permissions on newly uploaded boost folder.
Also ... if using FTP to transfer that folder, make sure you transfer using binary mode ... not ascii ... possible file corruption on upload might occur if using ascii mode.
After uploading the boost folder, comment out the line you added to config.php. Looks like:
Server should now use boost, no error or 'white screen of death' ... and you can investigate in-compatible themes at that point.
MR Ken Task
I will do and tell you the result