I tried to use the resize2fs for dev/sda1 and it didn't work for me.
Hi!
log in to ssh..
Try this:
df -hT (it will show what kind of partition you are using, ext3,ext4,XFS,etc)
then, if the 40GB additional space is already allocated to your vps, for you to use then you have to make your root partition to "grow"
growpart /dev/sda1 1
if your partition is XFS then..
xfs_growfs -d / (this will expand to all the root partition)
if not, you have to use resize..
hope this helps!