I have a Brother 98-Stitch Computerized Sewing & Embroidery Machine, SE270D. I dropped the feed dogs and now it wont come back up.

the slide switch could be broken, also could be a problem with the feed dogs, machine needs to be checked

It is likely that your feed dogs have been dropped. Try following the instructions listed in the attached link. It is also possible that something got jostled in shipping, and may need adjusting. If you can locate the feed dog drop mechanism and it is engaged, you may need to take your machine back to where you purchased it and have it replaced or adjusted.
How do raise or lower the feed dogs Brother

Replace the needle with a Schmetz needle. If that doesn't work you need to get it serviced

A manual feed is used primarily in freehand embroidery, quilting, and shoe repair. With manual feed, the stitch length and direction is controlled entirely by the motion of the material being sewn. Frequently some form of hoop or stabilizing material is used with fabric to keep the material under proper tension and aid in moving it around. Most household machines can be set for manual feed by disengaging the drop feed dogs. Most industrial machines can not be used for manual feed without actually removing the feed dogs.

sounds like there is something wrong with the feed dogs or the feed
dog lever could be broken,, they need to be checked

Drop your feed dogs, remove your normal foot... replace with embroidery or darning foot... or leave without a foot. stretch fabric in a hoop..... set your stitch.. and sew as you move the hoop.

check the feed dogs under the needle plate to see if there up or down
if there down then the feed dog switch need to be moved to the up position
but if there up,,,then the machine needs to be serviced so the feed dogs & stitches can be checked

Are you sure that the feed dogs have not been dropped to enable embroidery, and not returned to the normal sew position, consult the handbook for instructions.

The feed dogs come up as soon as you start sewing again. Just make sure they're in the up position and start sewing.

The embroidery carriage automatically lowers the feed dogs when put in place