PayPal being blocked by Anti-Virus/Secure Browser/AdBlockers? eg Kaspersky. Here's a quick tip
Security Systems are as secure as you make them
Security systems are great but if left unconfigured, they pose a problem in your daily lives.
So when using such system, it is advised to add trusted systems, such as PayPal or your Bank, to their exception list(whitelist). Otherwise payment flows on your favorite shopping site may be blocked by your security system. Please check your software providers website or contact them directly for guides how to do that.