One of the most common issues that faced anyone with a brand new drysuit is that the next seal is too tight. Trying to don it on will result on a purple face very soon and is not recommended. If you are using a latex or silicone seals, you will notice rings on them which are designed to be guides for you to cut along to loosen the seal.
However, before you reach for that scissors, try stretching that seal over a cylinder and let it sit for 24-48 hours; it might be enough to stretch it out so that you do not need to cut it.
Good luck and safe diving!