I would like to open this thread to discuss the SD-card subject and to centralize reports about SD-cards that works nicely, don’t work, have been counterfeited, etc.
To start the thread i have a first report about these 2 beauties that i just opened and burned with the intention of sending to several community members that have issues:
They seem good, right? Yes, i buy from amazon, from a “supposedly” trusted source. Indeed, i have ordered many sdcards from this merchant in the past and recently, including several 64GB sdcards in the same order.
I was surprised because of the white/grey combination, that i had not seem lately, but the real surprise has been when after burning, my zynthian V5 has refused to boot with both of them. I’ve repeated the burning. Nothing.
Then i opened this one and burned:
Same order and merchant. It worked like a charm at first try and i’m pretty sure it will work for years like the first days (i have some experience with this 
)
What is the difference? I couldn’t say. Of course, the color. The first ones are SDHC (32GB) and the second one is SDXC (64GB). But they all seems perfectly OK, both are UHS-1. Good quality packaging, good merchant, normal price. And both color combinations are legit.
I must admit that it’s been 3 years from the last time i bought “bad” sdcards, but i also must admit that i’ve been extremely picky and i’ve accepted to pay extra money to buy from trusted merchants.
Of course, I could do extra tests to the “bad” sdcards and spend a lot of time to know what the hell is happening, but the true is that such an effort wouldn’t improve my skills to not buying bad sdcards again. After years in the business, i’m still buying bad ones from time to time 
All i can say is.
- Be picky. Choose trusted sources.
- Pay the price
- Be prepared to fail
- so … don’t put all eggs in the same basket. I mean, buy several sd-cards of different models and sizes. 32 or 64 GB. I rarely buy nothing but sandisk, but you could try samsung, or so.
And don’t blame your zynthian V5 without being sure your sd-card is not guilty!! Remember that:
SD-cards are the main vector of issues with new zynthians.
All the best luck!!