Welcome to Vodafone Community
Are you able to speak to Vodafone customer services via 191 or Live Chat.
And or try clearing your browers cookies and cache and or try another compuet or browser.
Current Phone > Samsung Note 10+ 5G _256Gb > Model: SM-N976B.
Samsung One Ui / Pie.
Samsung Gear s3 Frontier Watch.
The problem is there is never ever a good time to do site maintenance. Hopefully Vodafone will have the page back online shortly. However, if you do not have a Vodafone number and able to use the 191 method to call, the contact numbers you need to contact Vodafone are on the link in your post.
TOBi, Vodafone's virtual agent, is online here Contact Us and will be able to put you in contact with the correct department to port in your number.
If you have any problems porting in your number, this will be something where the Team on the forum will be able to help.
I would say actually there is a good time to do maintenance - at 2am on Sunday morning when most people are liley to be in bed and not right in the middle of a work day. Although I do agree your IT enginners wouldn't want to work then, nor would Vodafone want to pay them overtime to work at that unsociable hour.