I'm 99% sure you're running into one of the
serious problems I ran into on
my project.
In my case, I had an old 200A main panel that had to become a new 200A "solar ready" main panel. Sunrun was my installer and submitted a work order with PG&E to approve a service disconnect so they could put in a new main service panel.
First, PG&E had routed the application to the wrong team in the local Planning department. Simple enough... I got my application re-routed.
Then, they bickered over whether the service coming to my house was 125A, 150A or 200A. PG&E's own line diagram for my specific neighborhood and house were inconsistent, and they didn't know the gauge cable underground of my house that was coming up to my PG&E meter. They had to send someone to my house to visually inspect what size service I had to determine if I was already 200A (easy peasy) or needed a service upgrade 150A to 200A (OUTRAGEOUSLY expensive).
After that, they bickered over whether this was simply a replacement of a "like for like" main panel. Newer building codes prohibit electrical items from sitting within 36 inches (measured square; not a radius) from the natural gas riser. Im my situation, the gas riser was sitting within 3 feet of my old main service panel since the code allowed that back when my house was constructed. The "like for like" provision allows a homeowner to replace their old main panel with a new main panel (say... 200A with a 200A) so long as they don't make the situation "less safe". This means they cannot move the main panel closer to the meter, and they cannot over-size the main panel compared to the previous panel. This is to allow reasonable projects without the homeowner having to pay the hefty costs to move the aperture that the main service resides and extend the big ol cables from PG&E to reach this new location.
The internal bickering at PG&E is whether or not going solar with batteries is considered an "upgrade" in all instances. Some people at PG&E think solar is a luxury item, so replacing a main service panel to allow a solar project is not within the scope of "like for like." These folks also believe that requiring the expensive lift-and-shift for the main service panel is the brass tax people need to pay to go green and "do things right." They insist the like for like program was only meant for a homeowner to replace old equipment because of age and damage; not to enhance their home.
I had to take it upon myself and work directly with PG&E on a solution. The corporations (Sunrun or Tesla) simply aren't equipped to handle this type of problem solving at the client-level. The corporate solution is to simply ask you to pay out the wazoooo for the upgrade, or just cancel your order. Assuming you actually want to move forward and this main panel is your obstacle, then you've got to do the work to unblock it... or find a different installer. Smaller shops tend to provide better service because they're more agile and motivated. Of course, a terrible small shop will still be terrible, so you'll still need to take care.
I wrote this up for reference on this specific topic in PG&E's area:
TLDR; if you don't like reading then you should just close this thread and move on. I've posted about my problems trying to get my "solar ready" main service panel (MSP) approved by PG&E. I'm consolidating some findings into this thread since it seems other people are having issues dealing...
teslamotorsclub.com
In summary, you need to determine if you really are getting a "main panel upgrade" or if it's more like a "main panel replacement."
The replacement is where you already have 200A service and a 200A main panel, but they're putting in a new 200A panel that is newer and more ready for the solar/batteries you may be getting. the like for like should apply if you're stubborn enough and it'll save you a lot of money.
It's hairier if your service is really being upgraded from 125A to 200A. If this is the case, then you will not qualify for the "like for like" provision since the upgraded service is deemed to be "less safe" due to the extra power involved.