Disable popup blockers
PayPal uses a safe encrypted popup [ example ]. If you use a popup blocker or antivirus software, disable temporary or creating an exception for hikearizona.com should work.

Try another browser ( several have reported success )
Chrome, Firefox, Android Chrome, and iPhone Safari should work.

Try another time
Like any site, PayPal is occasionally down. Most issues are reported overnight and early morning.

Note
PayPal does not require login. However, non-account holders that use PayPal can only use a particular credit card 15 times, and only up to a maximum of approximately $4,000 in a lifetime.