I have not been able to access my forum for the past dozen or so hours. I get a page not found error.
Forum is
http://solar-flux.forumandco.com/

Hi there, is this it?
http://solar-flux.forumotion.com/

It is. Why has the URL changed? Could it be returned so that links are not broken? (both links on the internet and for bookmarks).

Please read the following thread https://help.forumotion.com/t155249-only-topic-technical-maintenance-on-forumotion-domains

sadly the domain names will never be used again

Is there a way to send a mass e-mail to all members informing them of the change?

Hello @Hungry4Info

Please send me by PM the foundation email you used to create your forum and I will recover the link for you.

Best regards.

Please send me by PM the foundation email you used to create your forum and I will recover the link for you.

I'm not sure I understand. You want the e-mail associated with the SiteAdmin account that created the forum? It's been a decade since the forum was made, so it's been a bit. I apologise if this is a dumb question.

Yes @Hungry4Info you can send a news letter out to your members to tell them of the change of address.

 Admin control penal Settings:
ACP >> General Tab >>  Newsletter >> Write and send a news letter.

Sadly some members may have asked not to get news letter's on their profile so they may not get it as a Email.

Sadly there is nothing you or any one else can do the stop this as it's up to your members if they want them or not.

The old URL now redirects to the current URL.
Thank you very much to whoever facilitated this. I sincerely appreciate it.

May I mark this topic as solved, @Hungry4Info?

Indeed.