You can send it anytime.If keep on waiting ,you will surely get a rejection.Send them immediately.
Dont expect them to contact you .Its your fault.You should have checked the requirements before submitting the letter.Every thing is available on Cic website.
Duties section is the lifeline of the letter.
On the basis of your duties ,IRCC gives the points .
Also ensure that duties are not cut paste from the NoC ,and your letter covers atleast 70 percent of them.
Means if 10 duties mentioned in the NOC,atleast 7 should be there in your letter and that too not copied.
Make sure the new letter has all the details mentioned in work experience section -
https://www.canada.ca/en/immigration-refugees-citizenship/corporate/publications-manuals/operational-bulletins-manuals/permanent-residence/express-entry/applications-received-on-after-january-1-2016-completeness-check.html
Good luck