FTPS - LFTP problem

We have some trouble in my company with ftps access with a provider. Here is our configuration: - Ubuntu 14.04 - LFTP | Version 4.6.3a --- - Our_cert.crt - our_key.key - provider.crt - AuthorityRoot.crt - AuthorityRootCa.crt Certificate authority = GlobalSign

#/home/USER/.lftp/conf
set cmd:time-style "%Y%m%d%H%M"
set ftp:ssl-protect-list false
set net:timeout 30
set net:max-retries 1
set ftp:ssl-allow true
set ftp:ssl-protect-data false
set ssl:ca-file   AuthorityRoot.crt / AuthorityRootCa.crt (both file in one )  # i dont even know if this is correct
set ssl:cert-file our_cert.crt
set ssl:key-file  ourkey.key
set xfer:clobber on
set ssl:verify-certificate false

Our command:

lftp   -e "debug 9; source /home/USER/.lftp/conf ;ls ;quit"   -u username,pwd ftp://provider.com  -p PORT

But when we try to reach our provider, we have an error:

**** SSL_connect: sslv3 alert handshake failure

Our provider can see when we try to reach them, they can validate our cert but we cant validate their cert. Everything is ok on their side. --- Btw: Everything worked fine before yesterday when their certs was expired and they also switch CA. We just replace authorityRootCa.crt (the file with everything inside in the field ssl:ca-file) with the new one --- Can someone tell me where should we put our certs or what's wrong here? Should we add provider.crt in our file ourcert.crt?