I am facing the exact same issue after assigning floating IP to a droplet.
PING 159.89.XXX.XXX (159.89.XXX.XXX): 56 data bytes
Request timeout for icmpseq 0
Request timeout for icmpseq 1
Request timeout for icmpseq 2
Request timeout for icmpseq 3
Request timeout for icmp_seq 4
So, I followed above instructions and unassigned, then reassigned the floating IP, which worked for a minute. After couple of hours, it stopped working and gave the same result as above.
The droplet where I am facing this issue is:
8 GB Memory / 30 GB Disk / NYC3 - Ubuntu LEMP on 16.04
I need for this to work so that I can move the Floating IP to the new server I have created via snapshot and updated the server, but until this works on the existing server, I can not assign it to the new server.
Any help / guidance will be much appreciated.