How to talk to a former therapist?

Long story short; Ever since before quarantine, I've been regressing to a state similar to one I had when I started therapy. Six years of progress are suddenly falling away and I've been dealing with old symptoms again along side newer ones.
I got out of therapy less than a year ago because I could cope well enough on my own. However, now I'm very scared of myself and I don't have anyone around me to support me. I want to get in contact with my former therapist and be their patient again, but I don't know if that's even possible.
Has anyone else had to re-engage with a former therapist? How did you start and how did it go? Is it any different to starting with a new therapist?
(Of course, with the pandemic I don't intend to meet my former therapist in person, at least not for a while. I don't even think their office is open. I don't know if its appropriate to do this stuff over email or the phone, though.)

It's absolutely fine to contact your former therapist and say that symptoms have returned and you'd like to resume therapy. Many therapists are doing video sessions currently, which are not as good as in-person (for me, anyway), but are certainly much better than nothing, and you have the advantage of already knowing and having worked with this person.

It's much different than starting with a new therapist because you already have a relationship with this one. Most of the work of establishing trust and getting to know each other is already done. Call or email, whichever you feel more comfortable doing or whichever was the best way to reach them in the past.

Hope this is helpful.

You aren't back where you started. Nietzsche said: "When we are tired, we are attacked by ideas we conquered long ago." Assuming your therapist's personal circumstances haven't changed (e.g. if they had to move state) I'm sure they will be delighted to resume work with you during this difficult period

All the best