Have you followed the instructions shown at https://XXXwww.paypal.com/selfhelp/article/FAQ1933 ?
(Actual links are not allowed in answers so remove the XXX I inserted)
For example, to reset your password via email:
1. Go to www.paypal.com.
2. Click Log In at the top of the page.
3. Click Having trouble logging in? (*do NOT close out of this window or you'll need to restart the password reset process.)
4. Type the email address you use for PayPal and click Next.
5. Select Receive an email so we can confirm this is your account, and click Next.
6. Enter the 6-digit security code we sent to your email (you may need to check or junk or spam folder) and click Continue.
7. Select another way of confirming it's you, and click Next.
8. After going through this last security check, create a new password (type it twice) and click Update.
There are also instructions to reset via phone or text.