Is it possible you have overwritten the digits function?
>> which digits
C:\Program Files\MATLAB\R2020a\toolbox\symbolic\symbolic\digits.m
My R2020a file does not contain a line "for i=1:length(s)" anywhere in it. Your error message suggests it is line 3.
When I create a local digits function (saved in the current folder), I get the following error message.
Not enough input arguments.
Error in digits (line 3)
for i=1:length(s)
Error in sym (line 201)
S.Digits = digits;
Error in sympref>implementedSymprefs (line 154)
y = {'FourierParameters', sym([1,-1]), 'MuPAD', 'sym', {};...
Error in sympref (line 90)
iSymprefs = implementedSymprefs;
Error in symengine
Error in sym (line 200)
symengine;
Error in syms (line 227)
defined = sym(zeros(1, length(args)));
Warning: Failed to initialize symbolic preferences.
> In symengine
In sym (line 200)
In syms (line 227)
Not enough input arguments.
Error in digits (line 3)
for i=1:length(s)
Error in sym (line 201)
S.Digits = digits;
Error in syms (line 227)
defined = sym(zeros(1, length(args)));
