Surely you have come here looking for solutions and answers to a problem that occasionally occurs to Mac users. The truth is that we rarely have to worry about a problem of this type in our team, but it is true that sometimes they do happen and today we will see what it means.
In some cases, when installing an operating system or just after it, strange symbols appear on our Mac that we do not identify. In this case, the prohibited or prohibition symbol is another of the symbols that may appear when starting our Mac after a macOS installation.
What exactly does this prohibition sign mean?
Well, the circle with the bar in the middle that we all identify by the highway code as the forbidden sign on the Mac means that our startup disk has a Mac operating system but we cannot use it on our computer for some reason. This means that the installation was successful but that for some reason we cannot run it on our machine, either due to incompatibility of some kind, because our Mac does not support the system or something similar.
How can we solve this problem on our Mac
The solution in this case is very simple and we only have to reinstall the operating system on the Mac to get out of this failure. In all Mac models, the boot is completed when the Finder menu bar, the desktop and the Dock appear, so in this case what we have to try is to install the system again and for this we have to follow the same Previous steps.
We can use the key command option when starting the computer. We press Command + R with which we will be able to reinstall the most recent version of macOS that had been installed on our Mac (recommended by Apple itself in many cases) then we have the possibility to press Option + cmd + R with which we are going to update to the most recent version of macOS that is compatible with our Mac and finally the longest combination that would be Shift + Option + cmd + R with which we will reinstall the macOS that came with the Mac on a startup or the next available version.
Any of these options serve us in these cases, we hope you do not have to use them but if necessary here you have it.
Good!
Let's see if you can give me a hand, because I've been crazy for two weeks and I don't know what else to do ... I'll tell you:
I have a late 2011 Macbook Pro with High Sierra, I expanded the ram and now it was time to put an Ssd to make it go faster. The fact is that I decided to remove the cd and replace it with a ssd, so use this for the OS and leave the hdd for storage.
The steps that I followed were the following:
1- I removed the hdd and put the ssd in its place, enter system recovery (cmd + r), format the disk in APFS and installed the OS from the internet. Everything installed without a problem, but after a few hours I turned the computer back on and a forbidden symbol appeared. I researched on the forums what that symbol meant.
2- Formatting in Macos Plus (with registry) and installing the OS that comes by default on the computer (LION), and from there start updating to High Sierra, I knew that the process would be very slow, but I wanted to eliminate all the possible options.
All good, but again after a few reboots the forbidden symbol appears again.
3- I read in a forum that having changed the Ram could be the reason why it gave me a failure, well, I put the two original cards that came with the mac back in, but without any success, it appeared again. the forbidden symbol.
4- I read that it could be the flex cable of the hard disk, so I bought one, but before replacing it I decided to put the hdd back in its place to see if it was the cable or something else. Well, I installed the High Sierra in the hdd without problem and it works perfectly, so I doubt that the cable will fail only with the ssd but not with the hdd, I hope you tell me that it is, because if so, I will mount the cable and that's it!
5 - Conclusion, I know that there is something that I should do to the ssd that is escaping me, but I can't know what it is. Let's see if someone has been in the same situation and can enlighten me.
Thanks !!