Cross-check with another browser
Open the same URL in Chrome (or the system browser). If that works, the site is fine and the problem is the current browser (often Edge).
Clear browsing data
In the failing browser: Menu → Settings → Privacy and security → Clear browsing data → at least Cached images and files → clear, then reopen. This usually fixes it.
Still stuck
Temporarily turn off Secure DNS / network protection in that browser, or switch to Chrome. Prefer Android 10+ and an updatable browser. Full steps: Help Center Devices and access.