I cannot offer any advice.
I can offer some observations. In particular, I can tell you that the burden is on the applicant to prove at least 1095 days of actual physical presence in Canada during the "eligibility period," that is, during the five years immediately preceding the date the applicant made the application. Falling short of that will require the application to be rejected.
FALLING SHORT BY JUST ONE DAY WILL RESULT IN THE APPLICATION BEING DENIED.
There is NO discretion to grant citizenship, in the context of the standard Section 5(1) grant citizenship application, if the applicant is short, even if by just one day.
So how it will go will depend on whether you can sufficiently document actual physical presence for at least, at the very least, 1095 days.
If you review ALL your information and it shows you will be short, at all short, there is NO point, none at all, in proceeding with this application. Withdrawing would be the sensible approach.
If you review ALL your information and compare it to what you know about IRCC's calculation, and you still believe your evidence shows you were indeed physically present at least 1095 days (or entitled to credit adding up to 1095 days if your Presence Calculation includes some credit, at the half day rate, for time in Canada prior to becoming a PR), it's your call, your judgment, as to whether you think it is worth continuing the process.
That is going to be awhile. It appears that so far, until now, IRCC will not have so much as looked at what you submitted in March 2020. And it may be months more before they even resume processing at that level.
You do not say what sort of request you got from IRCC. That can matter. Whether it is a CIT 0520 or a CIT 0171. Or some other form of request.
If what YOU submitted also shows you fall short (again, even by a day), it may be possible that a Citizenship Officer can deny the application without the case being bogged down in a referral to a Citizenship Judge hearing. That would be the quickest result (but that could still take a long time, especially this year). I am not sure this is how it works. Generally contested presence cases go to a Citizenship Judge.
If what YOU submitted is strong evidence showing that you did in fact meet the 1095 day minimum presence requirement, a Citizenship Officer can make a favourable decision. The lawyer's opinion makes me suspect this is not the situation.
If you claim 1095 or more days IN Canada while IRCC believes it was 1094 days or fewer, that is a contested presence case which must be decided by a Citizenship Judge (unless you withdraw first) and that process takes a long, long time in the BEST of TIMES. I cannot even imagine how long it will take for a case just at the beginning stage of RQ (Residency Questionnaire) processing during this year . . . another YEAR? Maybe longer?
So even if you think you have a decent case, it might be prudent to withdraw and start over . . . but of course that could depend in large part whether you have continued to be IN Canada. That is, if you have continued to live in Canada and mostly stay in Canada since applying, and thus would clearly have well over the 1095 day minimum, it may indeed be more prudent, AND FASTER, to withdraw and start over, even if you believe you have a decent case to show at least 1095 days under the current application.
REMEMBER: for purposes of the current application, days in Canada after applying do not help. They do not get counted.