OpenVPN Error

We have been succesfully connecting to a Netgear R8000 (FW: V1.03.46_1.1.32) router using OpenVPN since August 2017. Recently, we could not connect and we did not make any changes to the OpenVPN software. We are not sure what version of the software we were using because we uninstalled it before looking at that or the logs ;(  So we decided to download the latest version 2.4.5 and replace our config files with fresh copy from the router. We got this error on connection attempt:

 WARNING: No server certificate verification method has been enabled.
OpenSSL: error:140AB18E:SSL routines:SSL_CTX_use_certificate:ca md too weak
OpenSSL reproted a certificate with a weak hash, please the in app FAQ about weak hashes
Cannot load inline certificate file
Exiting due to fatal error

We decided to go back a version of OpenVPN to  2.4.3 and we could connect ok.  How can we get version 2.4.5 to work-it must be more secure.

Thank you!