Had trouble with err_ssl_protocol_error on Chrome with a new setup for Remote Access VPN web login firepower(with fmc) and asa. But it worked fine on Firefox
It turns out that Chrome currently do not support Elliptical Curve Diffie-Hellman Group Group21 - 521-bit EC. Changing the ssl setting to Group20 - 384-bit EC fixed the issue.
Took me a long while to figure out. I hope someone else can save some time.