Why am I unable to generate more than 1 random string?

My code here will always generate one string of length MAXLEN but then start generating strings with a lower length. I'm not certain of why this is happening.

void generate_strings(int n) {
    char genvals[] = "abcdefghijklmnopqrstuvwxyzABC"
                     "DEFGHIJKLMNOPQRSTUVWXYZ0123456789 ";
    char str[MAXLEN + 1];
    int i = 0, j = 0;
    for (i = 0; i < n; i++) {
        for (int j = 0; j < MAXLEN; j++) {
            str[j] = genvals[rand() % strlen(genvals) - 1];
        }
        str[MAXSTRLEN] = '\0';
        printf("%s\n", str);
        memset(str, 0, MAXLEN);
    }

}