ip6 bridge mode

My XB8 stopped responding to ipv6 solicit messages when in bridge mode. That happened sometime yesterday or the day before. It works fine when the modem is not in bridge mode although what changed in that case is that it responds with "No prefix available" when the router requests prefix delegation /60. I tried with all lengths between 56 and 64 and the response is universally - no prefix available. But at least when not in bridge mode, I get v6 IP. When in bridge mode, the modem doesn't respond anymore to dhcp6 solicit messages anymore. Can someone help?