Almost 14 months after submission the associate editor informed me they still did not start with the review process Few days ago I received an email from the associate editor. He apologized for my paper has mistakenly been left outside of the normal review process. This happened almost 14 months after my submission. I asked the journal editor for information on the status of the review process about 7 months ago and received an email from the technical staff that my status is "in review" as can be seen in Editorial Manager system. The journal is highly ranked and the review process usually takes a long time. So, I thought everything was ok. The associate editor is asking me now if I still want to proceed this submission. Should I say yes?
Unfortunately, these things happen, and it sounds like the journal is at least being appropriately apologetic.

If you go do a different journal, you'll be starting all over again.  If this is a good journal for your field, and you think it's an honest mistake, then I would instead recommend asking for an expedited review process.  Since the editors are acknowledging they messed things up, you are likely to get faster and better consideration from them than another equivalent peer journal.

So: be collegial and gracious about their mistake, and next time you'll have good reason for when you send an earlier status query.