I have a paper in submission and only managed to revise it after more than 8 months when I emailed the editor a reminder about my paper. I have re-submitted my paper about a month ago but from the website status regarding my paper, an invitation on my revised manuscript had been sent to the reviewer and is waiting for him/her to accept it. Is it reasonable to ask the editor to send a reminder email to the reviewer again and if so, how should I phrase it?
I suggest that it won't lead to any change. It will be a bit of noise for the editor. Probably not especially irritating, but it adds to their load and someone will need (perhaps) to take time to respond to you. When everyone does this, and many want to, the system slows down.
If the editor is at all competent, they haven't forgotten you and have some process already in place for finding, prodding, reminding reviewers as they think warranted.
Unless you have some real need, beyond anxiety, to know something, I suggest patience. Work on the next thing, perhaps.
You can, but it might not be very helpful. The reason is that Editorial Management Systems (i.e. whatever software is used to tell you what the status is) will typically send automated reminders. Your reviewer simply isn't accepting the invitation in spite of being reminded.
For the editor the alternative is to invite a fresh reviewer, which is not ideal for a revised paper.
If you do decide to ask the journal to send a reminder, write to the journal office. It's something they should be able to handle. I personally wouldn't say "please send a reminder", but rather ask them for a generic status update. The status you're seeing is somewhat more detailed than is common, so you write something like "is the reviewer not accepting the invitation?".