This has already once been discussed here Initial Install Password Error .
So the problem with VROPS is, that once installed it will keep all informations within vCenter or the Host, and getting it away is what is really difficult.
However not impossible. Check on the Disks (Datastores) and search for the vGuest name you named vROPS vGuest.
Delete all entries that you find, after that please run this commands on the vCenter:
Check first for all running services:
service-control --stop --all
Check afterwards to see that all are running again, or maybe some more are running:
Do not yet reinstall.
Search on all Datastores for remaining copyies of the vROPS installation again.
Make sure that there are no leftovers.
Download a new version of vROPS or the previouse one.
Install if from scratch, use another name that you used before, use another IP adress and so on, everything new.
Create a PW that follows this, at least 1 Capital, normal letter, 1 number or a special sign and make it at least 8 digit long.
If this keeps failing, reboot the vCenter and try again.
Out of curiosity why are you installing 6.1 and not 6.6.1
I had the same problem and after many hours, I found the solution :
1- login to console and it it says that you must change the password, so I changed the password
2- back to wizard and go with new password