Apple
To clear cookies and cache on Safari, on an iPhone or iPad, go to Settings > Safari and tap Clear History and Website Data to remove everything at once, or go to Settings > Safari > Advanced > Website Data to delete individually. On a Mac, open Safari, go to the Safari menu > Settings > Privacy, then click Manage Website Data to find and delete all or specific site data.
On iPhone or iPad
Open the Settings app on your device.
Scroll down and tap on Safari.
To clear all history, cache, and cookies, scroll to the bottom and tap Clear History and Website Data.
Confirm your choice by tapping Clear History and Website Data again.
This video demonstrates how to clear the cache and cookies on an iPhone: How to clear the history, cache, and cookies from Safari on iPhone and iPad | Apple Support
On Mac
Open Safari.
In the top-left corner, click the Safari menu.
Select Settings (or Preferences on older macOS versions).
Click the Privacy tab.
Click Manage Website Data.
To remove all cached data, click Remove All, then confirm by clicking Remove Now.
To remove data from specific websites, scroll through the list, select the websites you want to remove, and then click Remove.
Click Done when finished and close the Settings window.
This video shows how to clear the history, cache, and cookies on a Mac:
Chrome / Android
To clear cookies and cache in Chrome on a computer, click the More menu icon (three dots) in the top-right corner, select Clear browsing data, choose the desired time range (like "All time"), check the boxes for "Cookies and other site data" and "Cached images and files," then click Clear data.
Step-by-step guide for desktop:
Open Chrome: on your computer.
Click the More icon (the three dots) in the top-right corner of the browser window.
Hover over More tools or directly click on Clear browsing data.
In the "Clear browsing data" window, select the Time range for the data you want to delete (e.g., Last hour, 24 hours, or All time), click Advanced to have more control.
Make sure the checkboxes for "Cookies and other site data" and "Cached images and files" are selected but if you want to save your stored passwords, make sure you do not check
Click the Clear data button to remove the selected information.
For Android phones and tablets:
Open the Chrome app on your Android device.
Tap the More icon (three dots) at the top right.
Tap History, then select Clear browsing data.
Choose a Time range from the top, such as "All time".
Check the boxes next to "Cookies and site data" and "Cached images and files".
Tap Clear data.
How test
If you still have a problem login in you can try ...
Test in Incognito Mode:
Open the website in an Incognito window
If you can login in Incognito, it suggests a browser extension or cached data is the problem so please repeat the steps above or,
Disable Browser Extensions:
Temporarily disable all your extensions to check if a conflicting extension is causing the error.