Ram updated from 4gb to 8gb, it only shows 4gb of ram in my ubuntu & 8gb of ram in BIOS

Product- Notebook 15-g002ax (HP 15 notebook laptop) 64bit

OS- Ubuntu 20.04.2 LTS

Memory shows- 3.3 GiB

amd processor, REV: 22CE-100

New ram: Hynix HMT41GS6BFR8A-PB, 8192 MB @ 800MHz (SODIMM DDR3)

I used to have 4gb of default ram in bank0(slot0) [bank1 is non customer usable] therefore i have bought 8gb of single ram. Removed 4gb of default ram & connected new 8gb ram in bank0.

but if i check in system it only show 3.3gb of ram just like before. And if i check in BIOS it shows 8gb ram.

1. Can i utilize 8 gb of ram on my system ?
2. is it compatible issue ? should i get back to my old perfectly working 4gb ram since the new 8gb ram not giving me enhanced performance ?

command outputs:

free -h output:

              total        used        free      shared  buff/cache   available
Mem:          3.3Gi       2.6Gi       156Mi        57Mi       568Mi       440Mi
Swap:         975Mi       386Mi       589Mi

lshw -c memory:

*-firmware                
       description: BIOS
       vendor: Insyde
       physical id: 0
       version: F.14
       date: 05/05/2014
       size: 128KiB
       capacity: 8MiB
       capabilities: pci upgrade shadowing cdboot bootselect socketedrom edd int13floppynec int13floppytoshiba int13floppy360 int13floppy1200 int13floppy720 int13floppy2880 int9keyboard int10video acpi usb uefi
  *-memory
       description: System Memory
       physical id: 10
       slot: System board or motherboard
       size: 8GiB
     *-bank:0
          description: SODIMM DDR3 Synchronous Unbuffered (Unregistered) 800 MHz (1.2 ns)
          product: HMT41GS6BFR8A-PB
          vendor: Hynix
          physical id: 0
          serial: 049C65FB
          slot: Bottom
          size: 8GiB
          width: 64 bits
          clock: 800MHz (1.2ns)
     *-bank:1
          description: SODIMM [empty]
          product: Empty
          vendor: Empty
          physical id: 1
          serial: Empty
          slot: Top

dmidecode -t memory

# dmidecode 3.2
Getting SMBIOS data from sysfs.
SMBIOS 2.7 present.

Handle 0x0010, DMI type 16, 23 bytes
Physical Memory Array
    Location: System Board Or Motherboard
    Use: System Memory
    Error Correction Type: None
    Maximum Capacity: 8 GB
    Error Information Handle: Not Provided
    Number Of Devices: 2

Handle 0x0011, DMI type 17, 34 bytes
Memory Device
    Array Handle: 0x0010
    Error Information Handle: Not Provided
    Total Width: 64 bits
    Data Width: 64 bits
    Size: 8192 MB
    Form Factor: SODIMM
    Set: None
    Locator: Bottom
    Bank Locator: CHANNEL A
    Type: DDR3
    Type Detail: Synchronous Unbuffered (Unregistered)
    Speed: 800 MT/s
    Manufacturer: Hynix
    Serial Number: 049C65FB
    Asset Tag: Asset Tag: 
    Part Number: HMT41GS6BFR8A-PB  
    Rank: 2
    Configured Memory Speed: 800 MT/s

Handle 0x0014, DMI type 17, 34 bytes
Memory Device
    Array Handle: 0x0010
    Error Information Handle: Not Provided
    Total Width: Unknown
    Data Width: Unknown
    Size: No Module Installed
    Form Factor: SODIMM
    Set: None
    Locator: Top
    Bank Locator: CHANNEL A
    Type: Unknown
    Type Detail: Unknown
    Speed: Unknown
    Manufacturer: Empty
    Serial Number: Empty
    Asset Tag: Asset Tag: 
    Part Number: Empty
    Rank: Unknown
    Configured Memory Speed: Unknown

The issue is been solved it was faulty ram sold to me by the local store and connected it in my absence. today i've replaced it(after lot of argument) with new one and it works perfectly fine and 8GB shows in my system. THANK YOU FOR YOUR ALL SUPPORT.

here's the new free -h output.

              total        used        free      shared  buff/cache   available
Mem:          6.7Gi       1.6Gi       2.7Gi        24Mi       2.4Gi       4.8Gi
Swap:         975Mi          0B       975Mi

There may be something wrong with that RAM module. The Hynix HMT41GS6BFR8A-PB is a DDR3L module that operates at 1600MHz. If you are seeing only 800MHz and half the storage (minus the dedicated graphics memory), then either the module is not receiving the correct voltage, the module is not seated in its memory slot correctly, or there is a hardware failure.

Consider testing the RAM using Memtest and, if errors are reported, include a photo of the test results when exchanging/returning the module