install.lock error

Hi,

have upgraded from v 3.53 to v 3.7.1 this is not my first upgrade have done before a few times.
after upload of files i keep getting the following message

Install pages have been disabled for security reason (by lock file install.lock into dolibarr root directory).
Click on following link. If you always reach this page, you must remove install.lock file manually.
Click here to go to Dolibarr

Have looked in root and documents folder, and searched for install.lock there is no such file, i know i can delete and re install from scratch but any ideas appreciated.

update;

found install.lock in documents folder deleted and upgrade was done.