This has been coming and going for various people of late.
I have been affected in the past, but not seen any problems more recently.
Reporting it to Enta resulted in it being fixed, but they claimed they'd done nothing and made no changes.
If it happens here it is always from 8am to 8pm that it doesn't work, so it's clearly something to do with the throttling settings Enta use to prioritise Business users during the day.
UKFSN via Entanet