Reinstalled MacOS on MacBookPro (Model early 2015) to Yosemite 10.10

macOS 10.10 is too old for accessing most websites today. You can try using a third party browser, but most of the current versions no longer support macOS 10.10 (you would need to find an older version of a third party browser which may still work to access the website, or a specially backported browser to work with macOS 10.10).

Another option is to install macOS 10.11 El Capitan. You can use any computer or OS capable of accessing the Internet to download the macOS 10.11 installer, then transfer it to this laptop where you will need to run the .pkg file to extract the real full installer to the Applications folder. Once the real installer is extracted into the Applicatons folder, you just need to run the "Install OS X El Capitan" app to upgrade to macOS 10.11. From there you can download & install macOS 10.13 - 12.x from the App Store.

Here is an Apple article with instructions for downloading & extracting various macOS installers....make sure to read the instructions carefully since the macOS 10.12 & earlier installers require multiple steps to extract the real installer to the Applications folder as I have already described.

How to download and install macOS - Apple Support

I highly recommend you create a bootable macOS USB installer so you have more options just in case something goes wrong so it will allow you to start at macOS 10.11 next time. Here is an Apple article with instructions for creating a bootable macOS USB installer:

Create a bootable installer for macOS - Apple Support

If macOS 10.12.6 has previously been installed on this laptop, then theoretically you should be able to access the online macOS 12.x Monterey installer by booting into Internet Recovery Mode using Command + Option + R. Unfortunately for some unknown reason some Macs will just boot to the online installer for the OS which originally shipped with the Mac from the factory regardless of the keys used for accessing recovery mode. Also, currently it appears that the older online macOS installers may no longer be working (10.7 through 10.13 for sure, and possibly even 10.14 & 10.15). There have been numerous reports for the last several weeks. Some of the regular contributors have notified Apple, but nothing appears to have changed, nor have we heard of any status updates regarding the issue.

if you have a working 10.10 Yosemite, simply apply all pending software updates, and you will get safari version 9 in the process.

SSL to TLS:

In 2015, researchers discovered that Secure Socket Layer (SSL) Internet encryption was not nearly as secure as was thought, and needed to be replaced. Internet encryption quickly moved to Transport Layer Security (TLS) which was rapidly deployed across the Internet. Over time, sites tightened requirements for what was acceptable for encryption.

Apple issued Safari version 9 in 10.11 El Capitan version of MacOS, which included TLS encryption. It was later provided by Security Update into the two previous versions of MacOS. 10.10 Yosemite and 10.9 Mavericks, PROVIDED you applied all available software updates.

MacOS versions older than those can not make a lot of secure [httpS:] connections on the Internet, because by todays standard, your proffered SSL encryption is considered inadequate.

JRsiMac Said:

"Reinstalled MacOS on MacBookPro (Model early 2015) to Yosemite 10.10: Message after reinstalling macOS on MacBookPro (early 2015) and connected to the Internet.: "Safari Can't Open the Page, Safari can't establish a secure connection to the server www.(any webpage address)". Any help? Thank you. JRsiMac"

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Getting Into a Secure Site:

A. Secure Shell:

Whats the protocol at the beginning of the URL? HTTPS? or HHTP? HTTPS uses secure shell encryption.

B. Create a New User:

So, create and use another User, seeing if you still get this error.

C. Restart the Mac:

Try restarting the Mac, seeing if that fixes this. Typically, you need to performa restart after making any major change to it, such as a reinstall or update install.

D. Add this as a Bookmark:

Using another device, try adding this as a bot may. Then, enable Safari in iCloud Settings on it. Once enabled, endless Safari in iCloud Settings on this Mac. See if it is seen in your history.

E. Clearing Temporary Internet Files:

Reset Safari once more, but this time in Safe Mode:

First, Boot into Safe Mode and then Clear your Temporary Internet Files of Safari:

1. Booting into Safe Mode: [hold down shift upon boot until the login screen appears]. See if this is still an issue. Safe Mode lets items run as default, without changes whatsoever. That is possible because caches of your macOS are temporarily disabled while in Safe Mode
2. Clearing your Temporary Internet Files (Cookies & Cache) of Safari: Cookies perform remembrance of certain site-entered data. Whereas Cache keeps a snapshot of the last time you visited a site.  Use this Link: Clearing History and Cache - Apple Communities

JRsiMac wrote:

For the benefit of readers, I had erased this little-used Laptop when on turning it on I saw a black screen, a keyboard in the upper right and voice instructions that seemed very suspicious. (A virus? Don't know.)

macOS will provide audio instructions for the visually impaired if the user doesn't begin interacting with Setup Assistant after a minute. Perfectly normal.