Why does pip3 install suddenly not work with a virtual environment - pip

Question

I am working on a python package using a virtual environment on Mac OS version 11.1 . I use the following command to create the virtual environment.
python3 -m venv .venv
Then I use this command to activate the virtual environment;
source .venv/bin/activate
I have used virtual environments in packages many times and have never had a problem. Suddenly with I try a pip install, lets say pip3 install NumPy the install fails with a massive error description. The first few lines state the following;
ERROR: Command errored out with exit status 1:
command: /Users/jonwebb/Desktop/Code_Dev/Python/core_utilities/.venv/bin/python3 /Users/jonwebb/Desktop/Code_Dev/Python/core_utilities/.venv/lib/python3.9/site-packages/pip/_vendor/pep517/_in_process.py build_wheel /var/folders/rb/11zk766j0jngjmv3qmvcfg7c0000gn/T/tmpc_rc8z1m
cwd: /private/var/folders/rb/11zk766j0jngjmv3qmvcfg7c0000gn/T/pip-install-bx_8yuq0/numpy
Complete output (2154 lines):
Running from numpy source directory.
numpy/random/_bounded_integers.pxd.in has not changed
numpy/random/_philox.pyx has not changed
numpy/random/_bounded_integers.pyx.in has not changed
numpy/random/_sfc64.pyx has not changed
numpy/random/_mt19937.pyx has not changed
numpy/random/bit_generator.pyx has not changed
Processing numpy/random/_bounded_integers.pyx
numpy/random/mtrand.pyx has not changed
numpy/random/_generator.pyx has not changed
numpy/random/_pcg64.pyx has not changed
numpy/random/_common.pyx has not changed
Cythonizing sources
blas_opt_info:
blas_mkl_info:
customize UnixCCompiler
libraries mkl_rt not found in ['/Users/jonwebb/Desktop/Code_Dev/Python/core_utilities/.venv/lib', '/usr/local/lib', '/usr/lib']
NOT AVAILABLE
blis_info:
libraries blis not found in ['/Users/jonwebb/Desktop/Code_Dev/Python/core_utilities/.venv/lib', '/usr/local/lib', '/usr/lib']
NOT AVAILABLE
openblas_info:
libraries openblas not found in ['/Users/jonwebb/Desktop/Code_Dev/Python/core_utilities/.venv/lib', '/usr/local/lib', '/usr/lib']
NOT AVAILABLE
atlas_3_10_blas_threads_info:
Setting PTATLAS=ATLAS
libraries tatlas not found in ['/Users/jonwebb/Desktop/Code_Dev/Python/core_utilities/.venv/lib', '/usr/local/lib', '/usr/lib']
NOT AVAILABLE
atlas_3_10_blas_info:
libraries satlas not found in ['/Users/jonwebb/Desktop/Code_Dev/Python/core_utilities/.venv/lib', '/usr/local/lib', '/usr/lib']
NOT AVAILABLE
atlas_blas_threads_info:
Setting PTATLAS=ATLAS
libraries ptf77blas,ptcblas,atlas not found in ['/Users/jonwebb/Desktop/Code_Dev/Python/core_utilities/.venv/lib', '/usr/local/lib', '/usr/lib']
NOT AVAILABLE
atlas_blas_info:
libraries f77blas,cblas,atlas not found in ['/Users/jonwebb/Desktop/Code_Dev/Python/core_utilities/.venv/lib', '/usr/local/lib', '/usr/lib']
NOT AVAILABLE
/private/var/folders/rb/11zk766j0jngjmv3qmvcfg7c0000gn/T/pip-install-bx_8yuq0/numpy/numpy/distutils/system_info.py:1989: UserWarning:
The last few lines look like;
########### CLIB COMPILER OPTIMIZATION ###########
Platform :
Architecture: x64
Compiler : clang
CPU baseline :
Requested : 'min'
Enabled : SSE SSE2 SSE3
Flags : -msse -msse2 -msse3
Extra checks: none
CPU dispatch :
Requested : 'max -xop -fma4'
Enabled : SSSE3 SSE41 POPCNT SSE42 AVX F16C FMA3 AVX2 AVX512F AVX512CD AVX512_KNL AVX512_SKX AVX512_CLX AVX512_CNL AVX512_ICL
Generated : none
CCompilerOpt._cache_write[796] : write cache to path -> /private/var/folders/rb/11zk766j0jngjmv3qmvcfg7c0000gn/T/pip-install-bx_8yuq0/numpy/build/temp.macosx-11-x86_64-3.9/ccompiler_opt_cache_clib.py
----------------------------------------
ERROR: Failed building wheel for numpy
Failed to build numpy
ERROR: Could not build wheels for numpy which use PEP 517 and cannot be installed directly
Until recently this was not a problem and I can still conduct pip3 installs outside of a virtual environment. Does anyone know what the cause of this issue is?