OC 2.3.0.2 Step 3 Install Error

Am trying to create a 2.0 Install on a test server.

Have created a fresh DB.

Installed OC files and start through the /install process. I get to Step 3 and enter all the login information for DB/User.

I receive the following error:
"Access denied for user 'testuser'@'localhost' (using password: YES)"

I have made sure permissions on config/admin config are 755.

I have used an auto generated password, as well as an easy one I can type.
I have also deleted and recreated user to make sure all permissions are selected.

Any ideas?

Is your database in the same server as your web server?

Yes it is.
Test site, will be under main site as subfolder.

For fun, I went ahead and tried a new /different browser and it went through install process. Any idea why that would have happened to allow that?

I exited the different browser and switched back to main browser and I now see an upgrade script when I navigate to subfolder/test url?

Was that a fresh install on a new folder?

Yes, although I have used the subfolder before for a test. Yesterday, I tried to clone a 1.5 store and then upgrade over it with 2.3.0.2. I was unable to make it work. I deleted the DB I created then, and the subfolder totally. Today I had the idea to use a 100% fresh 2.0 install and then migrate data over using import/export tool.

I can navigate to test site, and test site admin, in different browser, and it functions as it should.
I hid the install directory, to prevent it coming up.
I cleared cookies on the main browser I use and when I navigate to site.com/subfolder, I receive a page not found error. I suspect that is because I hid the install folder, after completing install on other browser.

On the primary domain I have it htaccessed, so that all traffic is https, and all urls (site.com, http://www.site.com) point to, https://www.site.com

So there was more to it after all. Migrations are tricky with OC, I'm a developer and I dont trust scripts to do them alone, knowing the lack of data integrity and often violation of database and file settings that extensions and mods perform.

Yeah it is incredibly weird. I have blocked/cleared all cookies, and auto complete from history from www.site.com in main browser and it still has the not found error/cant access test site. I guess for now, until I can get it fixed I will keep accessing the site from the other browser.