I am also having the same issue, I opened a ticket for the same. Yet to get a working solution from DO support since last 4 days. First I was asked to power off the machine and then try to resize, but that did not work. Then I was told to unmount the volume and resize, that too didn’t work. Now I am waiting for DO’s solution.

I have received an answer from my Support Ticket. The tutorial needs updating with at least two steps to be done prior to the tutorial’s steps.

1) Shutdown the droplet
sudo shutdown -h now

2) Refresh the Droplet page in order to refresh the Volume page, then disconnect the Volume from the Droplet using the pulldown (which will then no longer be grey).

3) Follow the tutorial at:
https://www.digitalocean.com/community/tutorials/how-to-increase-the-size-of-a-digitalocean-block-storage-volume

0) During this process I got a corrupted filesystem – I do not know the fault as it could have been something that I did. But I suggest that you backup your Volume offsite as a first step.

It all went smooth until the lsblk step, when I didn’t get a filetype or UUID back from the system. Later, at the e2fsck step I got the following error. I report this here in case it happens to others so we can get a history to the Support team:

sudo e2fsck -f /dev/disk/by-id/scsi-0DOVolumemysfo2volumename-part1
Bad magic number in super-block while trying to open /dev/disk/by-id/scsi-0DOVolumedownloads1-part1
Couldn’t find valid filesystem superblock.

Good luck

I found that I can resize the volume by detaching it from the droplet, then go to the volumes tab and then you will see the resize active.
Before detaching the volume, make sure you unmount it in the droplet to make sure you will not have any data corrupted.

Great solution!