Once your tax return status changes to accepted it indicates that the IRS has "picked it up" so to speak from the mailbox. The IRS has it now.
The reasons for delays in processing are numerous. The #1 reason for delays this year is that many people filed their tax return before they allowed enough time for the second round of stimulus checks to arrive.
If what the IRS has on file for whether you did (or didn't) get a payment differs from what your return states your refund is suspended while the IRS computers mail you a letter and wait a required amount of time to allow you to respond. The IRS is very backed up. It will be a few weeks before your letter likely even gets mailed.
The USPS is backed up, too, so there could be some delays there. Unfortunately, there is nothing you can do but wait for the letter - no matter what the reason for it.
As an aside, until a few years ago it wasn't really a big deal to just file your return and be done with it as soon as you had your W-2 and other documents. However, these days there are just too many things happening, especially last minute, and too many opportunities for things that can make filing early slow things down (makes little sense, I know.)
For the future, consider waiting until around 10 days or so after the IRS begins accepting returns and you see people posting "I got my refund!" and then submit yours. You can prepare it before then, but try to wait a few days to submit to avoid the chance of getting stuck "processing". A few week delay may seem like a lot but consider this: there are still people who are waiting for their 2019 refunds because of similar issues.
The IRS customarily has a goal of 21 days, but it is taking longer this year. They are dealing with a huge backlog, in part because of all the extra returns filed this year just for the stimulus. Lots of folks, and not just TT users, are still waiting.