The first thing to check is the con-rods. This can stop or slow a fan from running.
It is common to knock these accidently in the first few weeks of ownership or when using for the first time in a season.
There is a good description in the manual or you can have a look at this page to get the con-rods correct
http://www.vulcanfan.com/troubleshooter.asp?brass=false
If that does not work, find/borrow a T10 torx screwdriver and check the 4 torx screws on the top plate are tight.
They need to be very tight. Tighten one of the screws just quarter of a turn, then its diagonal neighbour should be tightened quarter of a turn.
Repeat with the other pair. Keep doing this until all the screws tight.
If that does not work check the shaft at the back that goes up and down through the brass bush.
Rotate the fan round so you can check the shaft it should feel oily and not sticky.
If it isn't oily clean it with a kitchen paper towel until it is shiny.
Then put a SINGLE drop of oil it. DO NOT keep repeating.
Do not use WD40 oil or motor oil. Use a light machine oil such as 3 in 1.
Never oil anything else. DO NOT oil bearings and DO NOT the glass.
If none of those things work get in contact with us.