Close limit too long
The opener tries to keep pushing after the door reaches the floor, senses resistance and reverses.

Door movement
A door that comes almost all the way down and then bounces back up usually has a close limit or force setting issue, or it is meeting resistance near the floor. It is often fixable with adjustment, but the cause needs to be checked first.
Short answer
When a door reverses right at the bottom, the opener may think it has hit an obstruction. Common causes are a close limit set too far down, low force sensitivity, a new or thick bottom seal, an uneven floor or something on the threshold. Clear the floor and check the sensors, then have the limits checked by a technician.
The opener tries to keep pushing after the door reaches the floor, senses resistance and reverses.
A raised threshold, debris or uneven slab can stop the door earlier than expected.
A thicker seal changes the contact point and may need a limit adjustment. See weather seals.
Worn rollers or a tight track near the bottom can add resistance.
Describe what the door is doing when you call. A provider may ask follow-up questions, but a reliable price normally needs an on-site look rather than a phone-only quote.

Travel limits tell the opener where fully open and fully closed are.

Most doors have a bottom seal in a retainer along the bottom panel and perimeter stops along the sides and top of the frame.

Photo-eye sensors sit a few inches above the floor on each side of the door.
That usually means the opener senses resistance at the end of travel. A close limit set too long, a thick seal or a raised floor area are common causes.
Yes. A new seal may be thicker than the old one, so the door contacts the floor sooner. The close limit may need adjusting.
Many openers let owners adjust limits following the manual. Make small changes and test the safety reverse afterward. If unsure, book a technician.
An uneven slab can make one side of the door touch first, which some openers read as resistance. A threshold or adjusted seal may help.
The reversing itself is a safety response, but it leaves the door open. It also hints that settings or hardware need attention.
Repeated reversing adds wear. More importantly, attempts to fix it by turning up force can make the opener unsafe.

Call to schedule a technician visit with an independent provider who serves your area.