If you have kali, searchspolit is useful in addition to the exploits in MSF. I haven’t done this lab, but I assume it means “Public Exploits” more than just ones which have a metasploit file built for them.
If the exploits you’ve tried haven’t worked, it probably means that they aren’t the right ones and you need to keep looking. Generally, there isn’t an easier answer - a lot of CTF/Pentesting is simply trying things and seeing what works.