It also happens to us, but the Whmcs version is stable 7.10 only some clients are correct others since the solidcp installation the usage and bandwidth statistics are not updated

Is there any follow up with this issue, I just came across this same issue on our servers, I see that the actual packages are not updating since 2019 according to what whmcs is displaying. I thought this was an issue with whmcs, and I followed an article on how to check the update function in their disk usage report is working, I see it it going to the hostying table and recovering the statistics from the table, but after a bit of sniffing aroung, I see the whmcs module is actually responsible to update the whmcs tables from solid cp actual usages.. and it seems this is not happening. I am running whmcs 8.1.3 so it seems it is not an whmcs issue but rather related to the whmcs module possibly. any help would be appreciated, as I see this query has been outstanding for a few months here...

Another interesting outcome regarding the disk and bandwidth updating, I started to probe deeper into this, the solidcp server db had all the info in it, however whmcs had some old info, it just looked like there was an issue somewhere in the coding or something, I then compared the old whmcs module to the latest 1.1.2 to 1.1.3 I then saw there was a small variation, and there were functions in the page to update the info, so I added custom buttons to the admin screen to execute the one function which I copied, this and the modules log gave me information which was being totally missed, not sure when the functions were called in whmcs, probably the cron, but I found that whmcs logs were moaning about not finding users in solidcp, and this seemed to be where the script terminated without any errors other than this.

I then checked the user that was not found and what I found was that we had a product added for hosting to whmcs, but it could not find the corresponding product in whmcs and this generated this error. effectively there was the product in whmcs and the hosting package had not yet been created in solidcp. After checking I deleted this package as I saw it was related to some domains we moved to other hosting packages and just were left in whmcs after being terminated, the package was still in an active state (and this is where I think setting them to cancelled or terminated might have sorted the issue out, but i deleted them before i tested this.). I then manually reran the update function and found 2 more similar accts like this, which I also deleted from the system as they were old packages that should have been removed. Once these packages were removed, I again manually reran the function and BINGO the rest of the accts updated the bandwidth and diskspace stats.

In all honesty I think this function in the solidcp.php file needs to test to see if a product exists and just log an error and move on again, it seems to stumble when it picks up an error and terminates currently

I will test further and see if I can generate the error again. and will report back, but I would suggest checking the modules log for errors of this kind.