In the unlikely event that you had no self-employment income in 2020 your election would mean nothing and can be ignored.
In the alternative, what is the effective date of the plan? If it is 1/1/2021 or later, again, your election would mean nothing and can be ignored.
In the alternative, if the plan was effective some date in 2020, but the document allows for a separate effective date just for salary deferrals and that date is 1/1/2021 or later, again, your election would mean nothing and can be ignored.
Does one of these three scenarios fit your facts?