If you ever need to delete/clear the cache in Microsoft Edge Browser then please follow these steps to do so.
Click on the 'Menu icon' represented as 3 Horizontal dots in top Right-hand corner of Microsoft Edge page.
Click on Settings.
Scroll down till you see Clear browsing data, then click on 'Choose what to clear'.
By default the first 4 options will be selected, simply click on the 'Clear' button.
Microsoft Edge Cache should now be clear and you can continue to log onto Customer Portal etc.
If there is still an issue than you can select all options than select Clear again.