You can renew your ssl certificate directly from Login to your account - InfinityFree where you can select your expired domain and request for renew and you can also import automatically by clicking button on install automatically
Issue a new one through the client area. Alternatively this may be a browser issue, check on an SSL checker tool if it has actually expired and try clearing your cache.
If your old certificate has expired, but you already have obtained and install a new certificate that will expire in March, then everything is good and you don’t need to do anything else. Your new certificate will keep working until it expires in March, so you’ll want to renew the certificate some time before that happens.